Imported Upstream version 2.28.0
[platform/upstream/git.git] / builtin / checkout.c
index 8bdc927..af849c6 100644 (file)
@@ -1,27 +1,31 @@
+#define USE_THE_INDEX_COMPATIBILITY_MACROS
 #include "builtin.h"
-#include "config.h"
+#include "advice.h"
+#include "blob.h"
+#include "branch.h"
+#include "cache-tree.h"
 #include "checkout.h"
+#include "commit.h"
+#include "config.h"
+#include "diff.h"
+#include "dir.h"
+#include "ll-merge.h"
 #include "lockfile.h"
+#include "merge-recursive.h"
+#include "object-store.h"
 #include "parse-options.h"
 #include "refs.h"
-#include "commit.h"
+#include "remote.h"
+#include "resolve-undo.h"
+#include "revision.h"
+#include "run-command.h"
+#include "submodule.h"
+#include "submodule-config.h"
 #include "tree.h"
 #include "tree-walk.h"
-#include "cache-tree.h"
 #include "unpack-trees.h"
-#include "dir.h"
-#include "run-command.h"
-#include "merge-recursive.h"
-#include "branch.h"
-#include "diff.h"
-#include "revision.h"
-#include "remote.h"
-#include "blob.h"
+#include "wt-status.h"
 #include "xdiff-interface.h"
-#include "ll-merge.h"
-#include "resolve-undo.h"
-#include "submodule-config.h"
-#include "submodule.h"
 
 static const char * const checkout_usage[] = {
        N_("git checkout [<options>] <branch>"),
@@ -29,17 +33,45 @@ static const char * const checkout_usage[] = {
        NULL,
 };
 
+static const char * const switch_branch_usage[] = {
+       N_("git switch [<options>] [<branch>]"),
+       NULL,
+};
+
+static const char * const restore_usage[] = {
+       N_("git restore [<options>] [--source=<branch>] <file>..."),
+       NULL,
+};
+
 struct checkout_opts {
        int patch_mode;
        int quiet;
        int merge;
        int force;
        int force_detach;
+       int implicit_detach;
        int writeout_stage;
        int overwrite_ignore;
        int ignore_skipworktree;
        int ignore_other_worktrees;
        int show_progress;
+       int count_checkout_paths;
+       int overlay_mode;
+       int dwim_new_local_branch;
+       int discard_changes;
+       int accept_ref;
+       int accept_pathspec;
+       int switch_branch_doing_nothing_is_ok;
+       int only_merge_on_switching_branches;
+       int can_switch_when_in_progress;
+       int orphan_from_empty_tree;
+       int empty_pathspec_ok;
+       int checkout_index;
+       int checkout_worktree;
+       const char *ignore_unmerged_opt;
+       int ignore_unmerged;
+       int pathspec_file_nul;
+       const char *pathspec_from_file;
 
        const char *new_branch;
        const char *new_branch_force;
@@ -47,26 +79,41 @@ struct checkout_opts {
        int new_branch_log;
        enum branch_track track;
        struct diff_options diff_options;
+       char *conflict_style;
 
        int branch_exists;
        const char *prefix;
        struct pathspec pathspec;
+       const char *from_treeish;
        struct tree *source_tree;
 };
 
-static int post_checkout_hook(struct commit *old, struct commit *new,
+struct branch_info {
+       const char *name; /* The short name used */
+       const char *path; /* The full name of a real branch */
+       struct commit *commit; /* The named commit */
+       char *refname; /* The full name of the ref being checked out. */
+       struct object_id oid; /* The object ID of the commit being checked out. */
+       /*
+        * if not null the branch is detached because it's already
+        * checked out in this checkout
+        */
+       char *checkout;
+};
+
+static int post_checkout_hook(struct commit *old_commit, struct commit *new_commit,
                              int changed)
 {
        return run_hook_le(NULL, "post-checkout",
-                          oid_to_hex(old ? &old->object.oid : &null_oid),
-                          oid_to_hex(new ? &new->object.oid : &null_oid),
+                          oid_to_hex(old_commit ? &old_commit->object.oid : &null_oid),
+                          oid_to_hex(new_commit ? &new_commit->object.oid : &null_oid),
                           changed ? "1" : "0", NULL);
-       /* "new" can be NULL when checking out from the index before
+       /* "new_commit" can be NULL when checking out from the index before
           a commit exists. */
 
 }
 
-static int update_some(const unsigned char *sha1, struct strbuf *base,
+static int update_some(const struct object_id *oid, struct strbuf *base,
                const char *pathname, unsigned mode, int stage, void *context)
 {
        int len;
@@ -77,8 +124,8 @@ static int update_some(const unsigned char *sha1, struct strbuf *base,
                return READ_TREE_RECURSIVE;
 
        len = base->len + strlen(pathname);
-       ce = xcalloc(1, cache_entry_size(len));
-       hashcpy(ce->oid.hash, sha1);
+       ce = make_empty_cache_entry(&the_index, len);
+       oidcpy(&ce->oid, oid);
        memcpy(ce->name, base->buf, base->len);
        memcpy(ce->name + base->len, pathname, len - base->len);
        ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
@@ -94,9 +141,10 @@ static int update_some(const unsigned char *sha1, struct strbuf *base,
        if (pos >= 0) {
                struct cache_entry *old = active_cache[pos];
                if (ce->ce_mode == old->ce_mode &&
-                   !oidcmp(&ce->oid, &old->oid)) {
+                   !ce_intent_to_add(old) &&
+                   oideq(&ce->oid, &old->oid)) {
                        old->ce_flags |= CE_UPDATE;
-                       free(ce);
+                       discard_cache_entry(ce);
                        return 0;
                }
        }
@@ -107,7 +155,8 @@ static int update_some(const unsigned char *sha1, struct strbuf *base,
 
 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
 {
-       read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
+       read_tree_recursive(the_repository, tree, "", 0, 0,
+                           pathspec, update_some, NULL);
 
        /* update the index with the given tree's info
         * for all args, expanding wildcards, and exit
@@ -124,7 +173,8 @@ static int skip_same_name(const struct cache_entry *ce, int pos)
        return pos;
 }
 
-static int check_stage(int stage, const struct cache_entry *ce, int pos)
+static int check_stage(int stage, const struct cache_entry *ce, int pos,
+                      int overlay_mode)
 {
        while (pos < active_nr &&
               !strcmp(active_cache[pos]->name, ce->name)) {
@@ -132,6 +182,8 @@ static int check_stage(int stage, const struct cache_entry *ce, int pos)
                        return 0;
                pos++;
        }
+       if (!overlay_mode)
+               return 0;
        if (stage == 2)
                return error(_("path '%s' does not have our version"), ce->name);
        else
@@ -157,21 +209,27 @@ static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 }
 
 static int checkout_stage(int stage, const struct cache_entry *ce, int pos,
-                         const struct checkout *state)
+                         const struct checkout *state, int *nr_checkouts,
+                         int overlay_mode)
 {
        while (pos < active_nr &&
               !strcmp(active_cache[pos]->name, ce->name)) {
                if (ce_stage(active_cache[pos]) == stage)
-                       return checkout_entry(active_cache[pos], state, NULL);
+                       return checkout_entry(active_cache[pos], state,
+                                             NULL, nr_checkouts);
                pos++;
        }
+       if (!overlay_mode) {
+               unlink_entry(ce);
+               return 0;
+       }
        if (stage == 2)
                return error(_("path '%s' does not have our version"), ce->name);
        else
                return error(_("path '%s' does not have their version"), ce->name);
 }
 
-static int checkout_merged(int pos, const struct checkout *state)
+static int checkout_merged(int pos, const struct checkout *state, int *nr_checkouts)
 {
        struct cache_entry *ce = active_cache[pos];
        const char *path = ce->name;
@@ -206,7 +264,8 @@ static int checkout_merged(int pos, const struct checkout *state)
         * merge.renormalize set, too
         */
        status = ll_merge(&result_buf, path, &ancestor, "base",
-                         &ours, "ours", &theirs, "theirs", NULL);
+                         &ours, "ours", &theirs, "theirs",
+                         state->istate, NULL);
        free(ancestor.ptr);
        free(ours.ptr);
        free(theirs.ptr);
@@ -227,28 +286,145 @@ static int checkout_merged(int pos, const struct checkout *state)
         * (it also writes the merge result to the object database even
         * when it may contain conflicts).
         */
-       if (write_sha1_file(result_buf.ptr, result_buf.size,
-                           blob_type, oid.hash))
+       if (write_object_file(result_buf.ptr, result_buf.size, blob_type, &oid))
                die(_("Unable to add merge result for '%s'"), path);
        free(result_buf.ptr);
-       ce = make_cache_entry(mode, oid.hash, path, 2, 0);
+       ce = make_transient_cache_entry(mode, &oid, path, 2);
        if (!ce)
                die(_("make_cache_entry failed for path '%s'"), path);
-       status = checkout_entry(ce, state, NULL);
-       free(ce);
+       status = checkout_entry(ce, state, NULL, nr_checkouts);
+       discard_cache_entry(ce);
        return status;
 }
 
+static void mark_ce_for_checkout_overlay(struct cache_entry *ce,
+                                        char *ps_matched,
+                                        const struct checkout_opts *opts)
+{
+       ce->ce_flags &= ~CE_MATCHED;
+       if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
+               return;
+       if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
+               /*
+                * "git checkout tree-ish -- path", but this entry
+                * is in the original index but is not in tree-ish
+                * or does not match the pathspec; it will not be
+                * checked out to the working tree.  We will not do
+                * anything to this entry at all.
+                */
+               return;
+       /*
+        * Either this entry came from the tree-ish we are
+        * checking the paths out of, or we are checking out
+        * of the index.
+        *
+        * If it comes from the tree-ish, we already know it
+        * matches the pathspec and could just stamp
+        * CE_MATCHED to it from update_some(). But we still
+        * need ps_matched and read_tree_recursive (and
+        * eventually tree_entry_interesting) cannot fill
+        * ps_matched yet. Once it can, we can avoid calling
+        * match_pathspec() for _all_ entries when
+        * opts->source_tree != NULL.
+        */
+       if (ce_path_match(&the_index, ce, &opts->pathspec, ps_matched))
+               ce->ce_flags |= CE_MATCHED;
+}
+
+static void mark_ce_for_checkout_no_overlay(struct cache_entry *ce,
+                                           char *ps_matched,
+                                           const struct checkout_opts *opts)
+{
+       ce->ce_flags &= ~CE_MATCHED;
+       if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
+               return;
+       if (ce_path_match(&the_index, ce, &opts->pathspec, ps_matched)) {
+               ce->ce_flags |= CE_MATCHED;
+               if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
+                       /*
+                        * In overlay mode, but the path is not in
+                        * tree-ish, which means we should remove it
+                        * from the index and the working tree.
+                        */
+                       ce->ce_flags |= CE_REMOVE | CE_WT_REMOVE;
+       }
+}
+
+static int checkout_worktree(const struct checkout_opts *opts,
+                            const struct branch_info *info)
+{
+       struct checkout state = CHECKOUT_INIT;
+       int nr_checkouts = 0, nr_unmerged = 0;
+       int errs = 0;
+       int pos;
+
+       state.force = 1;
+       state.refresh_cache = 1;
+       state.istate = &the_index;
+
+       init_checkout_metadata(&state.meta, info->refname,
+                              info->commit ? &info->commit->object.oid : &info->oid,
+                              NULL);
+
+       enable_delayed_checkout(&state);
+       for (pos = 0; pos < active_nr; pos++) {
+               struct cache_entry *ce = active_cache[pos];
+               if (ce->ce_flags & CE_MATCHED) {
+                       if (!ce_stage(ce)) {
+                               errs |= checkout_entry(ce, &state,
+                                                      NULL, &nr_checkouts);
+                               continue;
+                       }
+                       if (opts->writeout_stage)
+                               errs |= checkout_stage(opts->writeout_stage,
+                                                      ce, pos,
+                                                      &state,
+                                                      &nr_checkouts, opts->overlay_mode);
+                       else if (opts->merge)
+                               errs |= checkout_merged(pos, &state,
+                                                       &nr_unmerged);
+                       pos = skip_same_name(ce, pos) - 1;
+               }
+       }
+       remove_marked_cache_entries(&the_index, 1);
+       remove_scheduled_dirs();
+       errs |= finish_delayed_checkout(&state, &nr_checkouts);
+
+       if (opts->count_checkout_paths) {
+               if (nr_unmerged)
+                       fprintf_ln(stderr, Q_("Recreated %d merge conflict",
+                                             "Recreated %d merge conflicts",
+                                             nr_unmerged),
+                                  nr_unmerged);
+               if (opts->source_tree)
+                       fprintf_ln(stderr, Q_("Updated %d path from %s",
+                                             "Updated %d paths from %s",
+                                             nr_checkouts),
+                                  nr_checkouts,
+                                  find_unique_abbrev(&opts->source_tree->object.oid,
+                                                     DEFAULT_ABBREV));
+               else if (!nr_unmerged || nr_checkouts)
+                       fprintf_ln(stderr, Q_("Updated %d path from the index",
+                                             "Updated %d paths from the index",
+                                             nr_checkouts),
+                                  nr_checkouts);
+       }
+
+       return errs;
+}
+
 static int checkout_paths(const struct checkout_opts *opts,
-                         const char *revision)
+                         const struct branch_info *new_branch_info)
 {
        int pos;
-       struct checkout state = CHECKOUT_INIT;
        static char *ps_matched;
        struct object_id rev;
        struct commit *head;
        int errs = 0;
        struct lock_file lock_file = LOCK_INIT;
+       int checkout_index;
+
+       trace2_cmd_mode(opts->patch_mode ? "patch" : "path");
 
        if (opts->track != BRANCH_TRACK_UNSPECIFIED)
                die(_("'%s' cannot be used with updating paths"), "--track");
@@ -256,8 +432,9 @@ static int checkout_paths(const struct checkout_opts *opts,
        if (opts->new_branch_log)
                die(_("'%s' cannot be used with updating paths"), "-l");
 
-       if (opts->force && opts->patch_mode)
-               die(_("'%s' cannot be used with updating paths"), "-f");
+       if (opts->ignore_unmerged && opts->patch_mode)
+               die(_("'%s' cannot be used with updating paths"),
+                   opts->ignore_unmerged_opt);
 
        if (opts->force_detach)
                die(_("'%s' cannot be used with updating paths"), "--detach");
@@ -265,18 +442,48 @@ static int checkout_paths(const struct checkout_opts *opts,
        if (opts->merge && opts->patch_mode)
                die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 
-       if (opts->force && opts->merge)
-               die(_("'%s' cannot be used with %s"), "-f", "-m");
+       if (opts->ignore_unmerged && opts->merge)
+               die(_("'%s' cannot be used with %s"),
+                   opts->ignore_unmerged_opt, "-m");
 
        if (opts->new_branch)
                die(_("Cannot update paths and switch to branch '%s' at the same time."),
                    opts->new_branch);
 
-       if (opts->patch_mode)
-               return run_add_interactive(revision, "--patch=checkout",
-                                          &opts->pathspec);
+       if (!opts->checkout_worktree && !opts->checkout_index)
+               die(_("neither '%s' or '%s' is specified"),
+                   "--staged", "--worktree");
+
+       if (!opts->checkout_worktree && !opts->from_treeish)
+               die(_("'%s' must be used when '%s' is not specified"),
+                   "--worktree", "--source");
+
+       if (opts->checkout_index && !opts->checkout_worktree &&
+           opts->writeout_stage)
+               die(_("'%s' or '%s' cannot be used with %s"),
+                   "--ours", "--theirs", "--staged");
+
+       if (opts->checkout_index && !opts->checkout_worktree &&
+           opts->merge)
+               die(_("'%s' or '%s' cannot be used with %s"),
+                   "--merge", "--conflict", "--staged");
+
+       if (opts->patch_mode) {
+               const char *patch_mode;
+
+               if (opts->checkout_index && opts->checkout_worktree)
+                       patch_mode = "--patch=checkout";
+               else if (opts->checkout_index && !opts->checkout_worktree)
+                       patch_mode = "--patch=reset";
+               else if (!opts->checkout_index && opts->checkout_worktree)
+                       patch_mode = "--patch=worktree";
+               else
+                       BUG("either flag must have been set, worktree=%d, index=%d",
+                           opts->checkout_worktree, opts->checkout_index);
+               return run_add_interactive(new_branch_info->name, patch_mode, &opts->pathspec);
+       }
 
-       hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
+       repo_hold_locked_index(the_repository, &lock_file, LOCK_DIE_ON_ERROR);
        if (read_cache_preload(&opts->pathspec) < 0)
                return error(_("index file corrupt"));
 
@@ -289,39 +496,17 @@ static int checkout_paths(const struct checkout_opts *opts,
         * Make sure all pathspecs participated in locating the paths
         * to be checked out.
         */
-       for (pos = 0; pos < active_nr; pos++) {
-               struct cache_entry *ce = active_cache[pos];
-               ce->ce_flags &= ~CE_MATCHED;
-               if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
-                       continue;
-               if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
-                       /*
-                        * "git checkout tree-ish -- path", but this entry
-                        * is in the original index; it will not be checked
-                        * out to the working tree and it does not matter
-                        * if pathspec matched this entry.  We will not do
-                        * anything to this entry at all.
-                        */
-                       continue;
-               /*
-                * Either this entry came from the tree-ish we are
-                * checking the paths out of, or we are checking out
-                * of the index.
-                *
-                * If it comes from the tree-ish, we already know it
-                * matches the pathspec and could just stamp
-                * CE_MATCHED to it from update_some(). But we still
-                * need ps_matched and read_tree_recursive (and
-                * eventually tree_entry_interesting) cannot fill
-                * ps_matched yet. Once it can, we can avoid calling
-                * match_pathspec() for _all_ entries when
-                * opts->source_tree != NULL.
-                */
-               if (ce_path_match(ce, &opts->pathspec, ps_matched))
-                       ce->ce_flags |= CE_MATCHED;
-       }
+       for (pos = 0; pos < active_nr; pos++)
+               if (opts->overlay_mode)
+                       mark_ce_for_checkout_overlay(active_cache[pos],
+                                                    ps_matched,
+                                                    opts);
+               else
+                       mark_ce_for_checkout_no_overlay(active_cache[pos],
+                                                       ps_matched,
+                                                       opts);
 
-       if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
+       if (report_path_error(ps_matched, &opts->pathspec)) {
                free(ps_matched);
                return 1;
        }
@@ -337,10 +522,11 @@ static int checkout_paths(const struct checkout_opts *opts,
                if (ce->ce_flags & CE_MATCHED) {
                        if (!ce_stage(ce))
                                continue;
-                       if (opts->force) {
-                               warning(_("path '%s' is unmerged"), ce->name);
+                       if (opts->ignore_unmerged) {
+                               if (!opts->quiet)
+                                       warning(_("path '%s' is unmerged"), ce->name);
                        } else if (opts->writeout_stage) {
-                               errs |= check_stage(opts->writeout_stage, ce, pos);
+                               errs |= check_stage(opts->writeout_stage, ce, pos, opts->overlay_mode);
                        } else if (opts->merge) {
                                errs |= check_stages((1<<2) | (1<<3), ce, pos);
                        } else {
@@ -354,32 +540,35 @@ static int checkout_paths(const struct checkout_opts *opts,
                return 1;
 
        /* Now we are committed to check them out */
-       state.force = 1;
-       state.refresh_cache = 1;
-       state.istate = &the_index;
+       if (opts->checkout_worktree)
+               errs |= checkout_worktree(opts, new_branch_info);
+       else
+               remove_marked_cache_entries(&the_index, 1);
 
-       enable_delayed_checkout(&state);
-       for (pos = 0; pos < active_nr; pos++) {
-               struct cache_entry *ce = active_cache[pos];
-               if (ce->ce_flags & CE_MATCHED) {
-                       if (!ce_stage(ce)) {
-                               errs |= checkout_entry(ce, &state, NULL);
-                               continue;
-                       }
-                       if (opts->writeout_stage)
-                               errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
-                       else if (opts->merge)
-                               errs |= checkout_merged(pos, &state);
-                       pos = skip_same_name(ce, pos) - 1;
-               }
-       }
-       errs |= finish_delayed_checkout(&state);
+       /*
+        * Allow updating the index when checking out from the index.
+        * This is to save new stat info.
+        */
+       if (opts->checkout_worktree && !opts->checkout_index && !opts->source_tree)
+               checkout_index = 1;
+       else
+               checkout_index = opts->checkout_index;
 
-       if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
-               die(_("unable to write new index file"));
+       if (checkout_index) {
+               if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
+                       die(_("unable to write new index file"));
+       } else {
+               /*
+                * NEEDSWORK: if --worktree is not specified, we
+                * should save stat info of checked out files in the
+                * index to avoid the next (potentially costly)
+                * refresh. But it's a bit tricker to do...
+                */
+               rollback_lock_file(&lock_file);
+       }
 
        read_ref_full("HEAD", 0, &rev, NULL);
-       head = lookup_commit_reference_gently(&rev, 1);
+       head = lookup_commit_reference_gently(the_repository, &rev, 1);
 
        errs |= post_checkout_hook(head, head, 0);
        return errs;
@@ -390,7 +579,7 @@ static void show_local_changes(struct object *head,
 {
        struct rev_info rev;
        /* I think we want full paths, even if we're in a subdirectory. */
-       init_revisions(&rev, NULL);
+       repo_init_revisions(the_repository, &rev, NULL);
        rev.diffopt.flags = opts->flags;
        rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
        diff_setup_done(&rev.diffopt);
@@ -406,16 +595,17 @@ static void describe_detached_head(const char *msg, struct commit *commit)
                pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
        if (print_sha1_ellipsis()) {
                fprintf(stderr, "%s %s... %s\n", msg,
-                       find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV), sb.buf);
+                       find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
        } else {
                fprintf(stderr, "%s %s %s\n", msg,
-                       find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV), sb.buf);
+                       find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
        }
        strbuf_release(&sb);
 }
 
 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
-                     int worktree, int *writeout_error)
+                     int worktree, int *writeout_error,
+                     struct branch_info *info)
 {
        struct unpack_trees_options opts;
        struct tree_desc tree_desc;
@@ -430,6 +620,9 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
        opts.verbose_update = o->show_progress;
        opts.src_index = &the_index;
        opts.dst_index = &the_index;
+       init_checkout_metadata(&opts.meta, info->refname,
+                              info->commit ? &info->commit->object.oid : &null_oid,
+                              NULL);
        parse_tree(tree);
        init_tree_desc(&tree_desc, tree->buffer, tree->size);
        switch (unpack_trees(1, &tree_desc, &opts)) {
@@ -449,21 +642,17 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
        }
 }
 
-struct branch_info {
-       const char *name; /* The short name used */
-       const char *path; /* The full name of a real branch */
-       struct commit *commit; /* The named commit */
-       /*
-        * if not null the branch is detached because it's already
-        * checked out in this checkout
-        */
-       char *checkout;
-};
-
 static void setup_branch_path(struct branch_info *branch)
 {
        struct strbuf buf = STRBUF_INIT;
 
+       /*
+        * If this is a ref, resolve it; otherwise, look up the OID for our
+        * expression.  Failure here is okay.
+        */
+       if (!dwim_ref(branch->name, strlen(branch->name), &branch->oid, &branch->refname))
+               repo_get_oid_committish(the_repository, branch->name, &branch->oid);
+
        strbuf_branchname(&buf, branch->name, INTERPRET_BRANCH_LOCAL);
        if (strcmp(buf.buf, branch->name))
                branch->name = xstrdup(buf.buf);
@@ -472,20 +661,27 @@ static void setup_branch_path(struct branch_info *branch)
 }
 
 static int merge_working_tree(const struct checkout_opts *opts,
-                             struct branch_info *old,
-                             struct branch_info *new,
+                             struct branch_info *old_branch_info,
+                             struct branch_info *new_branch_info,
                              int *writeout_error)
 {
        int ret;
        struct lock_file lock_file = LOCK_INIT;
+       struct tree *new_tree;
 
        hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
        if (read_cache_preload(NULL) < 0)
                return error(_("index file corrupt"));
 
        resolve_undo_clear();
-       if (opts->force) {
-               ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
+       if (opts->new_orphan_branch && opts->orphan_from_empty_tree) {
+               if (new_branch_info->commit)
+                       BUG("'switch --orphan' should never accept a commit as starting point");
+               new_tree = parse_tree_indirect(the_hash_algo->empty_tree);
+       } else
+               new_tree = get_commit_tree(new_branch_info->commit);
+       if (opts->discard_changes) {
+               ret = reset_tree(new_tree, opts, 1, writeout_error, new_branch_info);
                if (ret)
                        return ret;
        } else {
@@ -511,40 +707,55 @@ static int merge_working_tree(const struct checkout_opts *opts,
                topts.initial_checkout = is_cache_unborn();
                topts.update = 1;
                topts.merge = 1;
-               topts.gently = opts->merge && old->commit;
+               topts.quiet = opts->merge && old_branch_info->commit;
                topts.verbose_update = opts->show_progress;
                topts.fn = twoway_merge;
+               init_checkout_metadata(&topts.meta, new_branch_info->refname,
+                                      new_branch_info->commit ?
+                                      &new_branch_info->commit->object.oid :
+                                      &new_branch_info->oid, NULL);
                if (opts->overwrite_ignore) {
                        topts.dir = xcalloc(1, sizeof(*topts.dir));
                        topts.dir->flags |= DIR_SHOW_IGNORED;
                        setup_standard_excludes(topts.dir);
                }
-               tree = parse_tree_indirect(old->commit ?
-                                          &old->commit->object.oid :
+               tree = parse_tree_indirect(old_branch_info->commit ?
+                                          &old_branch_info->commit->object.oid :
                                           the_hash_algo->empty_tree);
                init_tree_desc(&trees[0], tree->buffer, tree->size);
-               tree = parse_tree_indirect(&new->commit->object.oid);
+               parse_tree(new_tree);
+               tree = new_tree;
                init_tree_desc(&trees[1], tree->buffer, tree->size);
 
                ret = unpack_trees(2, trees, &topts);
+               clear_unpack_trees_porcelain(&topts);
                if (ret == -1) {
                        /*
                         * Unpack couldn't do a trivial merge; either
                         * give up or do a real merge, depending on
                         * whether the merge flag was used.
                         */
-                       struct tree *result;
                        struct tree *work;
+                       struct tree *old_tree;
                        struct merge_options o;
+                       struct strbuf sb = STRBUF_INIT;
+                       struct strbuf old_commit_shortname = STRBUF_INIT;
+
                        if (!opts->merge)
                                return 1;
 
                        /*
-                        * Without old->commit, the below is the same as
+                        * Without old_branch_info->commit, the below is the same as
                         * the two-tree unpack we already tried and failed.
                         */
-                       if (!old->commit)
+                       if (!old_branch_info->commit)
                                return 1;
+                       old_tree = get_commit_tree(old_branch_info->commit);
+
+                       if (repo_index_has_changes(the_repository, old_tree, &sb))
+                               die(_("cannot continue with staged changes in "
+                                     "the following files:\n%s"), sb.buf);
+                       strbuf_release(&sb);
 
                        /* Do more real merge */
 
@@ -567,24 +778,35 @@ static int merge_working_tree(const struct checkout_opts *opts,
                         * a pain; plumb in an option to set
                         * o.renormalize?
                         */
-                       init_merge_options(&o);
+                       init_merge_options(&o, the_repository);
                        o.verbosity = 0;
-                       work = write_tree_from_memory(&o);
+                       work = write_in_core_index_as_tree(the_repository);
 
-                       ret = reset_tree(new->commit->tree, opts, 1,
-                                        writeout_error);
+                       ret = reset_tree(new_tree,
+                                        opts, 1,
+                                        writeout_error, new_branch_info);
                        if (ret)
                                return ret;
-                       o.ancestor = old->name;
-                       o.branch1 = new->name;
+                       o.ancestor = old_branch_info->name;
+                       if (old_branch_info->name == NULL) {
+                               strbuf_add_unique_abbrev(&old_commit_shortname,
+                                                        &old_branch_info->commit->object.oid,
+                                                        DEFAULT_ABBREV);
+                               o.ancestor = old_commit_shortname.buf;
+                       }
+                       o.branch1 = new_branch_info->name;
                        o.branch2 = "local";
-                       ret = merge_trees(&o, new->commit->tree, work,
-                               old->commit->tree, &result);
+                       ret = merge_trees(&o,
+                                         new_tree,
+                                         work,
+                                         old_tree);
                        if (ret < 0)
                                exit(128);
-                       ret = reset_tree(new->commit->tree, opts, 0,
-                                        writeout_error);
+                       ret = reset_tree(new_tree,
+                                        opts, 0,
+                                        writeout_error, new_branch_info);
                        strbuf_release(&o.obuf);
+                       strbuf_release(&old_commit_shortname);
                        if (ret)
                                return ret;
                }
@@ -599,26 +821,26 @@ static int merge_working_tree(const struct checkout_opts *opts,
        if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
                die(_("unable to write new index file"));
 
-       if (!opts->force && !opts->quiet)
-               show_local_changes(&new->commit->object, &opts->diff_options);
+       if (!opts->discard_changes && !opts->quiet && new_branch_info->commit)
+               show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
 
        return 0;
 }
 
-static void report_tracking(struct branch_info *new)
+static void report_tracking(struct branch_info *new_branch_info)
 {
        struct strbuf sb = STRBUF_INIT;
-       struct branch *branch = branch_get(new->name);
+       struct branch *branch = branch_get(new_branch_info->name);
 
-       if (!format_tracking_info(branch, &sb))
+       if (!format_tracking_info(branch, &sb, AHEAD_BEHIND_FULL))
                return;
        fputs(sb.buf, stdout);
        strbuf_release(&sb);
 }
 
 static void update_refs_for_switch(const struct checkout_opts *opts,
-                                  struct branch_info *old,
-                                  struct branch_info *new)
+                                  struct branch_info *old_branch_info,
+                                  struct branch_info *new_branch_info)
 {
        struct strbuf msg = STRBUF_INIT;
        const char *old_desc, *reflog_msg;
@@ -645,69 +867,70 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
                        free(refname);
                }
                else
-                       create_branch(opts->new_branch, new->name,
+                       create_branch(the_repository,
+                                     opts->new_branch, new_branch_info->name,
                                      opts->new_branch_force ? 1 : 0,
                                      opts->new_branch_force ? 1 : 0,
                                      opts->new_branch_log,
                                      opts->quiet,
                                      opts->track);
-               new->name = opts->new_branch;
-               setup_branch_path(new);
+               new_branch_info->name = opts->new_branch;
+               setup_branch_path(new_branch_info);
        }
 
-       old_desc = old->name;
-       if (!old_desc && old->commit)
-               old_desc = oid_to_hex(&old->commit->object.oid);
+       old_desc = old_branch_info->name;
+       if (!old_desc && old_branch_info->commit)
+               old_desc = oid_to_hex(&old_branch_info->commit->object.oid);
 
        reflog_msg = getenv("GIT_REFLOG_ACTION");
        if (!reflog_msg)
                strbuf_addf(&msg, "checkout: moving from %s to %s",
-                       old_desc ? old_desc : "(invalid)", new->name);
+                       old_desc ? old_desc : "(invalid)", new_branch_info->name);
        else
-               strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
+               strbuf_insertstr(&msg, 0, reflog_msg);
 
-       if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
+       if (!strcmp(new_branch_info->name, "HEAD") && !new_branch_info->path && !opts->force_detach) {
                /* Nothing to do. */
-       } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
-               update_ref(msg.buf, "HEAD", &new->commit->object.oid, NULL,
+       } else if (opts->force_detach || !new_branch_info->path) {      /* No longer on any branch. */
+               update_ref(msg.buf, "HEAD", &new_branch_info->commit->object.oid, NULL,
                           REF_NO_DEREF, UPDATE_REFS_DIE_ON_ERR);
                if (!opts->quiet) {
-                       if (old->path &&
+                       if (old_branch_info->path &&
                            advice_detached_head && !opts->force_detach)
-                               detach_advice(new->name);
-                       describe_detached_head(_("HEAD is now at"), new->commit);
+                               detach_advice(new_branch_info->name);
+                       describe_detached_head(_("HEAD is now at"), new_branch_info->commit);
                }
-       } else if (new->path) { /* Switch branches. */
-               if (create_symref("HEAD", new->path, msg.buf) < 0)
+       } else if (new_branch_info->path) {     /* Switch branches. */
+               if (create_symref("HEAD", new_branch_info->path, msg.buf) < 0)
                        die(_("unable to update HEAD"));
                if (!opts->quiet) {
-                       if (old->path && !strcmp(new->path, old->path)) {
+                       if (old_branch_info->path && !strcmp(new_branch_info->path, old_branch_info->path)) {
                                if (opts->new_branch_force)
                                        fprintf(stderr, _("Reset branch '%s'\n"),
-                                               new->name);
+                                               new_branch_info->name);
                                else
                                        fprintf(stderr, _("Already on '%s'\n"),
-                                               new->name);
+                                               new_branch_info->name);
                        } else if (opts->new_branch) {
                                if (opts->branch_exists)
-                                       fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
+                                       fprintf(stderr, _("Switched to and reset branch '%s'\n"), new_branch_info->name);
                                else
-                                       fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
+                                       fprintf(stderr, _("Switched to a new branch '%s'\n"), new_branch_info->name);
                        } else {
                                fprintf(stderr, _("Switched to branch '%s'\n"),
-                                       new->name);
+                                       new_branch_info->name);
                        }
                }
-               if (old->path && old->name) {
-                       if (!ref_exists(old->path) && reflog_exists(old->path))
-                               delete_reflog(old->path);
+               if (old_branch_info->path && old_branch_info->name) {
+                       if (!ref_exists(old_branch_info->path) && reflog_exists(old_branch_info->path))
+                               delete_reflog(old_branch_info->path);
                }
        }
-       remove_branch_state();
+       remove_branch_state(the_repository, !opts->quiet);
        strbuf_release(&msg);
        if (!opts->quiet &&
-           (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
-               report_tracking(new);
+           (new_branch_info->path || (!opts->force_detach && !strcmp(new_branch_info->name, "HEAD"))))
+               report_tracking(new_branch_info);
 }
 
 static int add_pending_uninteresting_ref(const char *refname,
@@ -721,7 +944,7 @@ static int add_pending_uninteresting_ref(const char *refname,
 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 {
        strbuf_addstr(sb, "  ");
-       strbuf_add_unique_abbrev(sb, commit->object.oid.hash, DEFAULT_ABBREV);
+       strbuf_add_unique_abbrev(sb, &commit->object.oid, DEFAULT_ABBREV);
        strbuf_addch(sb, ' ');
        if (!parse_commit(commit))
                pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
@@ -779,7 +1002,7 @@ static void suggest_reattach(struct commit *commit, struct rev_info *revs)
                        " git branch <new-branch-name> %s\n\n",
                        /* Give ngettext() the count */
                        lost),
-                       find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV));
+                       find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV));
 }
 
 /*
@@ -787,80 +1010,89 @@ static void suggest_reattach(struct commit *commit, struct rev_info *revs)
  * HEAD.  If it is not reachable from any ref, this is the last chance
  * for the user to do so without resorting to reflog.
  */
-static void orphaned_commit_warning(struct commit *old, struct commit *new)
+static void orphaned_commit_warning(struct commit *old_commit, struct commit *new_commit)
 {
        struct rev_info revs;
-       struct object *object = &old->object;
-       struct object_array refs;
+       struct object *object = &old_commit->object;
 
-       init_revisions(&revs, NULL);
+       repo_init_revisions(the_repository, &revs, NULL);
        setup_revisions(0, NULL, &revs, NULL);
 
        object->flags &= ~UNINTERESTING;
        add_pending_object(&revs, object, oid_to_hex(&object->oid));
 
        for_each_ref(add_pending_uninteresting_ref, &revs);
-       add_pending_oid(&revs, "HEAD", &new->object.oid, UNINTERESTING);
-
-       /* Save pending objects, so they can be cleaned up later. */
-       refs = revs.pending;
-       revs.leak_pending = 1;
+       if (new_commit)
+               add_pending_oid(&revs, "HEAD",
+                               &new_commit->object.oid,
+                               UNINTERESTING);
 
-       /*
-        * prepare_revision_walk (together with .leak_pending = 1) makes us
-        * the sole owner of the list of pending objects.
-        */
        if (prepare_revision_walk(&revs))
                die(_("internal error in revision walk"));
-       if (!(old->object.flags & UNINTERESTING))
-               suggest_reattach(old, &revs);
+       if (!(old_commit->object.flags & UNINTERESTING))
+               suggest_reattach(old_commit, &revs);
        else
-               describe_detached_head(_("Previous HEAD position was"), old);
+               describe_detached_head(_("Previous HEAD position was"), old_commit);
 
        /* Clean up objects used, as they will be reused. */
-       clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
-
-       object_array_clear(&refs);
+       clear_commit_marks_all(ALL_REV_FLAGS);
 }
 
 static int switch_branches(const struct checkout_opts *opts,
-                          struct branch_info *new)
+                          struct branch_info *new_branch_info)
 {
        int ret = 0;
-       struct branch_info old;
+       struct branch_info old_branch_info;
        void *path_to_free;
        struct object_id rev;
        int flag, writeout_error = 0;
-       memset(&old, 0, sizeof(old));
-       old.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
-       if (old.path)
-               old.commit = lookup_commit_reference_gently(&rev, 1);
+       int do_merge = 1;
+
+       trace2_cmd_mode("branch");
+
+       memset(&old_branch_info, 0, sizeof(old_branch_info));
+       old_branch_info.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
+       if (old_branch_info.path)
+               old_branch_info.commit = lookup_commit_reference_gently(the_repository, &rev, 1);
        if (!(flag & REF_ISSYMREF))
-               old.path = NULL;
+               old_branch_info.path = NULL;
 
-       if (old.path)
-               skip_prefix(old.path, "refs/heads/", &old.name);
+       if (old_branch_info.path)
+               skip_prefix(old_branch_info.path, "refs/heads/", &old_branch_info.name);
+
+       if (opts->new_orphan_branch && opts->orphan_from_empty_tree) {
+               if (new_branch_info->name)
+                       BUG("'switch --orphan' should never accept a commit as starting point");
+               new_branch_info->commit = NULL;
+               new_branch_info->name = "(empty)";
+               do_merge = 1;
+       }
 
-       if (!new->name) {
-               new->name = "HEAD";
-               new->commit = old.commit;
-               if (!new->commit)
+       if (!new_branch_info->name) {
+               new_branch_info->name = "HEAD";
+               new_branch_info->commit = old_branch_info.commit;
+               if (!new_branch_info->commit)
                        die(_("You are on a branch yet to be born"));
-               parse_commit_or_die(new->commit);
+               parse_commit_or_die(new_branch_info->commit);
+
+               if (opts->only_merge_on_switching_branches)
+                       do_merge = 0;
        }
 
-       ret = merge_working_tree(opts, &old, new, &writeout_error);
-       if (ret) {
-               free(path_to_free);
-               return ret;
+       if (do_merge) {
+               ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
+               if (ret) {
+                       free(path_to_free);
+                       return ret;
+               }
        }
 
-       if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
-               orphaned_commit_warning(old.commit, new->commit);
+       if (!opts->quiet && !old_branch_info.path && old_branch_info.commit && new_branch_info->commit != old_branch_info.commit)
+               orphaned_commit_warning(old_branch_info.commit, new_branch_info->commit);
 
-       update_refs_for_switch(opts, &old, new);
+       update_refs_for_switch(opts, &old_branch_info, new_branch_info);
 
-       ret = post_checkout_hook(old.commit, new->commit, 1);
+       ret = post_checkout_hook(old_branch_info.commit, new_branch_info->commit, 1);
        free(path_to_free);
        return ret || writeout_error;
 }
@@ -879,16 +1111,74 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
        return git_xmerge_config(var, value, NULL);
 }
 
+static void setup_new_branch_info_and_source_tree(
+       struct branch_info *new_branch_info,
+       struct checkout_opts *opts,
+       struct object_id *rev,
+       const char *arg)
+{
+       struct tree **source_tree = &opts->source_tree;
+       struct object_id branch_rev;
+
+       new_branch_info->name = arg;
+       setup_branch_path(new_branch_info);
+
+       if (!check_refname_format(new_branch_info->path, 0) &&
+           !read_ref(new_branch_info->path, &branch_rev))
+               oidcpy(rev, &branch_rev);
+       else
+               new_branch_info->path = NULL; /* not an existing branch */
+
+       new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
+       if (!new_branch_info->commit) {
+               /* not a commit */
+               *source_tree = parse_tree_indirect(rev);
+       } else {
+               parse_commit_or_die(new_branch_info->commit);
+               *source_tree = get_commit_tree(new_branch_info->commit);
+       }
+}
+
+static const char *parse_remote_branch(const char *arg,
+                                      struct object_id *rev,
+                                      int could_be_checkout_paths)
+{
+       int num_matches = 0;
+       const char *remote = unique_tracking_name(arg, rev, &num_matches);
+
+       if (remote && could_be_checkout_paths) {
+               die(_("'%s' could be both a local file and a tracking branch.\n"
+                       "Please use -- (and optionally --no-guess) to disambiguate"),
+                   arg);
+       }
+
+       if (!remote && num_matches > 1) {
+           if (advice_checkout_ambiguous_remote_branch_name) {
+                   advise(_("If you meant to check out a remote tracking branch on, e.g. 'origin',\n"
+                            "you can do so by fully qualifying the name with the --track option:\n"
+                            "\n"
+                            "    git checkout --track origin/<name>\n"
+                            "\n"
+                            "If you'd like to always have checkouts of an ambiguous <name> prefer\n"
+                            "one remote, e.g. the 'origin' remote, consider setting\n"
+                            "checkout.defaultRemote=origin in your config."));
+           }
+
+           die(_("'%s' matched multiple (%d) remote tracking branches"),
+               arg, num_matches);
+       }
+
+       return remote;
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
                                int dwim_new_local_branch_ok,
-                               struct branch_info *new,
+                               struct branch_info *new_branch_info,
                                struct checkout_opts *opts,
                                struct object_id *rev)
 {
-       struct tree **source_tree = &opts->source_tree;
        const char **new_branch = &opts->new_branch;
        int argcount = 0;
-       struct object_id branch_rev;
        const char *arg;
        int dash_dash_pos;
        int has_dash_dash = 0;
@@ -915,8 +1205,10 @@ static int parse_branchname_arg(int argc, const char **argv,
         *   (b) If <something> is _not_ a commit, either "--" is present
         *       or <something> is not a path, no -t or -b was given, and
         *       and there is a tracking branch whose name is <something>
-        *       in one and only one remote, then this is a short-hand to
-        *       fork local <something> from that remote-tracking branch.
+        *       in one and only one remote (or if the branch exists on the
+        *       remote named in checkout.defaultRemote), then this is a
+        *       short-hand to fork local <something> from that
+        *       remote-tracking branch.
         *
         *   (c) Otherwise, if "--" is present, treat it like case (1).
         *
@@ -936,10 +1228,16 @@ static int parse_branchname_arg(int argc, const char **argv,
        if (!argc)
                return 0;
 
+       if (!opts->accept_pathspec) {
+               if (argc > 1)
+                       die(_("only one reference expected"));
+               has_dash_dash = 1; /* helps disambiguate */
+       }
+
        arg = argv[0];
        dash_dash_pos = -1;
        for (i = 0; i < argc; i++) {
-               if (!strcmp(argv[i], "--")) {
+               if (opts->accept_pathspec && !strcmp(argv[i], "--")) {
                        dash_dash_pos = i;
                        break;
                }
@@ -950,6 +1248,7 @@ static int parse_branchname_arg(int argc, const char **argv,
                has_dash_dash = 1; /* case (3) or (1) */
        else if (dash_dash_pos >= 2)
                die(_("only one reference expected, %d given."), dash_dash_pos);
+       opts->count_checkout_paths = !opts->quiet && !has_dash_dash;
 
        if (!strcmp(arg, "-"))
                arg = "@{-1}";
@@ -965,19 +1264,24 @@ static int parse_branchname_arg(int argc, const char **argv,
                 */
                int recover_with_dwim = dwim_new_local_branch_ok;
 
-               if (!has_dash_dash &&
-                   (check_filename(opts->prefix, arg) || !no_wildcard(arg)))
+               int could_be_checkout_paths = !has_dash_dash &&
+                       check_filename(opts->prefix, arg);
+
+               if (!has_dash_dash && !no_wildcard(arg))
                        recover_with_dwim = 0;
+
                /*
-                * Accept "git checkout foo" and "git checkout foo --"
-                * as candidates for dwim.
+                * Accept "git checkout foo", "git checkout foo --"
+                * and "git switch foo" as candidates for dwim.
                 */
                if (!(argc == 1 && !has_dash_dash) &&
-                   !(argc == 2 && has_dash_dash))
+                   !(argc == 2 && has_dash_dash) &&
+                   opts->accept_pathspec)
                        recover_with_dwim = 0;
 
                if (recover_with_dwim) {
-                       const char *remote = unique_tracking_name(arg, rev);
+                       const char *remote = parse_remote_branch(arg, rev,
+                                                                could_be_checkout_paths);
                        if (remote) {
                                *new_branch = arg;
                                arg = remote;
@@ -999,26 +1303,11 @@ static int parse_branchname_arg(int argc, const char **argv,
        argv++;
        argc--;
 
-       new->name = arg;
-       setup_branch_path(new);
-
-       if (!check_refname_format(new->path, 0) &&
-           !read_ref(new->path, &branch_rev))
-               oidcpy(rev, &branch_rev);
-       else
-               new->path = NULL; /* not an existing branch */
-
-       new->commit = lookup_commit_reference_gently(rev, 1);
-       if (!new->commit) {
-               /* not a commit */
-               *source_tree = parse_tree_indirect(rev);
-       } else {
-               parse_commit_or_die(new->commit);
-               *source_tree = new->commit->tree;
-       }
+       setup_new_branch_info_and_source_tree(new_branch_info, opts, rev, arg);
 
-       if (!*source_tree)                   /* case (1): want a tree */
+       if (!opts->source_tree)                   /* case (1): want a tree */
                die(_("reference is not a tree: %s"), arg);
+
        if (!has_dash_dash) {   /* case (3).(d) -> (1) */
                /*
                 * Do not complain the most common case
@@ -1028,7 +1317,7 @@ static int parse_branchname_arg(int argc, const char **argv,
                 */
                if (argc)
                        verify_non_filename(opts->prefix, arg);
-       } else {
+       } else if (opts->accept_pathspec) {
                argcount++;
                argv++;
                argc--;
@@ -1042,6 +1331,8 @@ static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
        int status;
        struct strbuf branch_ref = STRBUF_INIT;
 
+       trace2_cmd_mode("unborn");
+
        if (!opts->new_branch)
                die(_("You are on a branch yet to be born"));
        strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
@@ -1053,8 +1344,62 @@ static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
        return status;
 }
 
+static void die_expecting_a_branch(const struct branch_info *branch_info)
+{
+       struct object_id oid;
+       char *to_free;
+
+       if (dwim_ref(branch_info->name, strlen(branch_info->name), &oid, &to_free) == 1) {
+               const char *ref = to_free;
+
+               if (skip_prefix(ref, "refs/tags/", &ref))
+                       die(_("a branch is expected, got tag '%s'"), ref);
+               if (skip_prefix(ref, "refs/remotes/", &ref))
+                       die(_("a branch is expected, got remote branch '%s'"), ref);
+               die(_("a branch is expected, got '%s'"), ref);
+       }
+       if (branch_info->commit)
+               die(_("a branch is expected, got commit '%s'"), branch_info->name);
+       /*
+        * This case should never happen because we already die() on
+        * non-commit, but just in case.
+        */
+       die(_("a branch is expected, got '%s'"), branch_info->name);
+}
+
+static void die_if_some_operation_in_progress(void)
+{
+       struct wt_status_state state;
+
+       memset(&state, 0, sizeof(state));
+       wt_status_get_state(the_repository, &state, 0);
+
+       if (state.merge_in_progress)
+               die(_("cannot switch branch while merging\n"
+                     "Consider \"git merge --quit\" "
+                     "or \"git worktree add\"."));
+       if (state.am_in_progress)
+               die(_("cannot switch branch in the middle of an am session\n"
+                     "Consider \"git am --quit\" "
+                     "or \"git worktree add\"."));
+       if (state.rebase_interactive_in_progress || state.rebase_in_progress)
+               die(_("cannot switch branch while rebasing\n"
+                     "Consider \"git rebase --quit\" "
+                     "or \"git worktree add\"."));
+       if (state.cherry_pick_in_progress)
+               die(_("cannot switch branch while cherry-picking\n"
+                     "Consider \"git cherry-pick --quit\" "
+                     "or \"git worktree add\"."));
+       if (state.revert_in_progress)
+               die(_("cannot switch branch while reverting\n"
+                     "Consider \"git revert --quit\" "
+                     "or \"git worktree add\"."));
+       if (state.bisect_in_progress)
+               warning(_("you are switching branch while bisecting"));
+}
+
 static int checkout_branch(struct checkout_opts *opts,
-                          struct branch_info *new)
+                          struct branch_info *new_branch_info)
 {
        if (opts->pathspec.nr)
                die(_("paths cannot be used with switching branches"));
@@ -1063,6 +1408,10 @@ static int checkout_branch(struct checkout_opts *opts,
                die(_("'%s' cannot be used with switching branches"),
                    "--patch");
 
+       if (opts->overlay_mode != -1)
+               die(_("'%s' cannot be used with switching branches"),
+                   "--[no]-overlay");
+
        if (opts->writeout_stage)
                die(_("'%s' cannot be used with switching branches"),
                    "--ours/--theirs");
@@ -1070,6 +1419,9 @@ static int checkout_branch(struct checkout_opts *opts,
        if (opts->force && opts->merge)
                die(_("'%s' cannot be used with '%s'"), "-f", "-m");
 
+       if (opts->discard_changes && opts->merge)
+               die(_("'%s' cannot be used with '%s'"), "--discard-changes", "--merge");
+
        if (opts->force_detach && opts->new_branch)
                die(_("'%s' cannot be used with '%s'"),
                    "--detach", "-b/-B/--orphan");
@@ -1077,27 +1429,46 @@ static int checkout_branch(struct checkout_opts *opts,
        if (opts->new_orphan_branch) {
                if (opts->track != BRANCH_TRACK_UNSPECIFIED)
                        die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
+               if (opts->orphan_from_empty_tree && new_branch_info->name)
+                       die(_("'%s' cannot take <start-point>"), "--orphan");
        } else if (opts->force_detach) {
                if (opts->track != BRANCH_TRACK_UNSPECIFIED)
                        die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
        } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
                opts->track = git_branch_track;
 
-       if (new->name && !new->commit)
+       if (new_branch_info->name && !new_branch_info->commit)
                die(_("Cannot switch branch to a non-commit '%s'"),
-                   new->name);
-
-       if (new->path && !opts->force_detach && !opts->new_branch &&
+                   new_branch_info->name);
+
+       if (!opts->switch_branch_doing_nothing_is_ok &&
+           !new_branch_info->name &&
+           !opts->new_branch &&
+           !opts->force_detach)
+               die(_("missing branch or commit argument"));
+
+       if (!opts->implicit_detach &&
+           !opts->force_detach &&
+           !opts->new_branch &&
+           !opts->new_branch_force &&
+           new_branch_info->name &&
+           !new_branch_info->path)
+               die_expecting_a_branch(new_branch_info);
+
+       if (!opts->can_switch_when_in_progress)
+               die_if_some_operation_in_progress();
+
+       if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
            !opts->ignore_other_worktrees) {
                int flag;
                char *head_ref = resolve_refdup("HEAD", 0, NULL, &flag);
                if (head_ref &&
-                   (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)))
-                       die_if_checked_out(new->path, 1);
+                   (!(flag & REF_ISSYMREF) || strcmp(head_ref, new_branch_info->path)))
+                       die_if_checked_out(new_branch_info->path, 1);
                free(head_ref);
        }
 
-       if (!new->commit && opts->new_branch) {
+       if (!new_branch_info->commit && opts->new_branch) {
                struct object_id rev;
                int flag;
 
@@ -1105,99 +1476,165 @@ static int checkout_branch(struct checkout_opts *opts,
                    (flag & REF_ISSYMREF) && is_null_oid(&rev))
                        return switch_unborn_to_new_branch(opts);
        }
-       return switch_branches(opts, new);
+       return switch_branches(opts, new_branch_info);
 }
 
-int cmd_checkout(int argc, const char **argv, const char *prefix)
+static struct option *add_common_options(struct checkout_opts *opts,
+                                        struct option *prevopts)
 {
-       struct checkout_opts opts;
-       struct branch_info new;
-       char *conflict_style = NULL;
-       int dwim_new_local_branch = 1;
        struct option options[] = {
-               OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
-               OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
-                          N_("create and checkout a new branch")),
-               OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
-                          N_("create/reset and checkout a branch")),
-               OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
-               OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
-               OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
-                       BRANCH_TRACK_EXPLICIT),
-               OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
-               OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
-                           2),
-               OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
-                           3),
-               OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
-               OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
-               OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
-               OPT_STRING(0, "conflict", &conflict_style, N_("style"),
+               OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+               OPT_CALLBACK_F(0, "recurse-submodules", NULL,
+                           "checkout", "control recursive updating of submodules",
+                           PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater),
+               OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+               OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+               OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
                           N_("conflict style (merge or diff3)")),
-               OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
-               OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
-                        N_("do not limit pathspecs to sparse entries only")),
-               OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
-                               N_("second guess 'git checkout <no-such-branch>'")),
-               OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+               OPT_END()
+       };
+       struct option *newopts = parse_options_concat(prevopts, options);
+       free(prevopts);
+       return newopts;
+}
+
+static struct option *add_common_switch_branch_options(
+       struct checkout_opts *opts, struct option *prevopts)
+{
+       struct option options[] = {
+               OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+               OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
+                       BRANCH_TRACK_EXPLICIT),
+               OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
+                          PARSE_OPT_NOCOMPLETE),
+               OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+               OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
+                          N_("update ignored files (default)"),
+                          PARSE_OPT_NOCOMPLETE),
+               OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
                         N_("do not check if another worktree is holding the given ref")),
-               { OPTION_CALLBACK, 0, "recurse-submodules", NULL,
-                           "checkout", "control recursive updating of submodules",
-                           PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-               OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
-               OPT_END(),
+               OPT_END()
        };
+       struct option *newopts = parse_options_concat(prevopts, options);
+       free(prevopts);
+       return newopts;
+}
 
-       memset(&opts, 0, sizeof(opts));
-       memset(&new, 0, sizeof(new));
-       opts.overwrite_ignore = 1;
-       opts.prefix = prefix;
-       opts.show_progress = -1;
+static struct option *add_checkout_path_options(struct checkout_opts *opts,
+                                               struct option *prevopts)
+{
+       struct option options[] = {
+               OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
+                             N_("checkout our version for unmerged files"),
+                             2, PARSE_OPT_NONEG),
+               OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
+                             N_("checkout their version for unmerged files"),
+                             3, PARSE_OPT_NONEG),
+               OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
+               OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
+                        N_("do not limit pathspecs to sparse entries only")),
+               OPT_PATHSPEC_FROM_FILE(&opts->pathspec_from_file),
+               OPT_PATHSPEC_FILE_NUL(&opts->pathspec_file_nul),
+               OPT_END()
+       };
+       struct option *newopts = parse_options_concat(prevopts, options);
+       free(prevopts);
+       return newopts;
+}
+
+/* create-branch option (either b or c) */
+static char cb_option = 'b';
+
+static int checkout_main(int argc, const char **argv, const char *prefix,
+                        struct checkout_opts *opts, struct option *options,
+                        const char * const usagestr[])
+{
+       struct branch_info new_branch_info;
+       int parseopt_flags = 0;
+
+       memset(&new_branch_info, 0, sizeof(new_branch_info));
+       opts->overwrite_ignore = 1;
+       opts->prefix = prefix;
+       opts->show_progress = -1;
 
-       git_config(git_checkout_config, &opts);
+       git_config(git_checkout_config, opts);
 
-       opts.track = BRANCH_TRACK_UNSPECIFIED;
+       opts->track = BRANCH_TRACK_UNSPECIFIED;
 
-       argc = parse_options(argc, argv, prefix, options, checkout_usage,
-                            PARSE_OPT_KEEP_DASHDASH);
+       if (!opts->accept_pathspec && !opts->accept_ref)
+               BUG("make up your mind, you need to take _something_");
+       if (opts->accept_pathspec && opts->accept_ref)
+               parseopt_flags = PARSE_OPT_KEEP_DASHDASH;
 
-       if (opts.show_progress < 0) {
-               if (opts.quiet)
-                       opts.show_progress = 0;
+       argc = parse_options(argc, argv, prefix, options,
+                            usagestr, parseopt_flags);
+
+       if (opts->show_progress < 0) {
+               if (opts->quiet)
+                       opts->show_progress = 0;
                else
-                       opts.show_progress = isatty(2);
+                       opts->show_progress = isatty(2);
        }
 
-       if (conflict_style) {
-               opts.merge = 1; /* implied */
-               git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
+       if (opts->conflict_style) {
+               opts->merge = 1; /* implied */
+               git_xmerge_config("merge.conflictstyle", opts->conflict_style, NULL);
+       }
+       if (opts->force) {
+               opts->discard_changes = 1;
+               opts->ignore_unmerged_opt = "--force";
+               opts->ignore_unmerged = 1;
        }
 
-       if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
-               die(_("-b, -B and --orphan are mutually exclusive"));
+       if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)
+               die(_("-%c, -%c and --orphan are mutually exclusive"),
+                               cb_option, toupper(cb_option));
+
+       if (opts->overlay_mode == 1 && opts->patch_mode)
+               die(_("-p and --overlay are mutually exclusive"));
+
+       if (opts->checkout_index >= 0 || opts->checkout_worktree >= 0) {
+               if (opts->checkout_index < 0)
+                       opts->checkout_index = 0;
+               if (opts->checkout_worktree < 0)
+                       opts->checkout_worktree = 0;
+       } else {
+               if (opts->checkout_index < 0)
+                       opts->checkout_index = -opts->checkout_index - 1;
+               if (opts->checkout_worktree < 0)
+                       opts->checkout_worktree = -opts->checkout_worktree - 1;
+       }
+       if (opts->checkout_index < 0 || opts->checkout_worktree < 0)
+               BUG("these flags should be non-negative by now");
+       /*
+        * convenient shortcut: "git restore --staged [--worktree]" equals
+        * "git restore --staged [--worktree] --source HEAD"
+        */
+       if (!opts->from_treeish && opts->checkout_index)
+               opts->from_treeish = "HEAD";
 
        /*
         * From here on, new_branch will contain the branch to be checked out,
         * and new_branch_force and new_orphan_branch will tell us which one of
-        * -b/-B/--orphan is being used.
+        * -b/-B/-c/-C/--orphan is being used.
         */
-       if (opts.new_branch_force)
-               opts.new_branch = opts.new_branch_force;
+       if (opts->new_branch_force)
+               opts->new_branch = opts->new_branch_force;
 
-       if (opts.new_orphan_branch)
-               opts.new_branch = opts.new_orphan_branch;
+       if (opts->new_orphan_branch)
+               opts->new_branch = opts->new_orphan_branch;
 
-       /* --track without -b/-B/--orphan should DWIM */
-       if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
+       /* --track without -c/-C/-b/-B/--orphan should DWIM */
+       if (opts->track != BRANCH_TRACK_UNSPECIFIED && !opts->new_branch) {
                const char *argv0 = argv[0];
                if (!argc || !strcmp(argv0, "--"))
-                       die (_("--track needs a branch name"));
+                       die(_("--track needs a branch name"));
                skip_prefix(argv0, "refs/", &argv0);
                skip_prefix(argv0, "remotes/", &argv0);
                argv0 = strchr(argv0, '/');
                if (!argv0 || !argv0[1])
-                       die (_("Missing branch name; try -b"));
-               opts.new_branch = argv0 + 1;
+                       die(_("missing branch name; try -%c"), cb_option);
+               opts->new_branch = argv0 + 1;
        }
 
        /*
@@ -1213,58 +1650,221 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
         * including "last branch" syntax and DWIM-ery for names of
         * remote branches, erroring out for invalid or ambiguous cases.
         */
-       if (argc) {
+       if (argc && opts->accept_ref) {
                struct object_id rev;
                int dwim_ok =
-                       !opts.patch_mode &&
-                       dwim_new_local_branch &&
-                       opts.track == BRANCH_TRACK_UNSPECIFIED &&
-                       !opts.new_branch;
+                       !opts->patch_mode &&
+                       opts->dwim_new_local_branch &&
+                       opts->track == BRANCH_TRACK_UNSPECIFIED &&
+                       !opts->new_branch;
                int n = parse_branchname_arg(argc, argv, dwim_ok,
-                                            &new, &opts, &rev);
+                                            &new_branch_info, opts, &rev);
                argv += n;
                argc -= n;
+       } else if (!opts->accept_ref && opts->from_treeish) {
+               struct object_id rev;
+
+               if (get_oid_mb(opts->from_treeish, &rev))
+                       die(_("could not resolve %s"), opts->from_treeish);
+
+               setup_new_branch_info_and_source_tree(&new_branch_info,
+                                                     opts, &rev,
+                                                     opts->from_treeish);
+
+               if (!opts->source_tree)
+                       die(_("reference is not a tree: %s"), opts->from_treeish);
        }
 
        if (argc) {
-               parse_pathspec(&opts.pathspec, 0,
-                              opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
+               parse_pathspec(&opts->pathspec, 0,
+                              opts->patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
                               prefix, argv);
 
-               if (!opts.pathspec.nr)
+               if (!opts->pathspec.nr)
                        die(_("invalid path specification"));
 
                /*
                 * Try to give more helpful suggestion.
                 * new_branch && argc > 1 will be caught later.
                 */
-               if (opts.new_branch && argc == 1)
+               if (opts->new_branch && argc == 1 && !new_branch_info.commit)
                        die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
-                               argv[0], opts.new_branch);
+                               argv[0], opts->new_branch);
 
-               if (opts.force_detach)
+               if (opts->force_detach)
                        die(_("git checkout: --detach does not take a path argument '%s'"),
                            argv[0]);
+       }
+
+       if (opts->pathspec_from_file) {
+               if (opts->pathspec.nr)
+                       die(_("--pathspec-from-file is incompatible with pathspec arguments"));
+
+               if (opts->force_detach)
+                       die(_("--pathspec-from-file is incompatible with --detach"));
+
+               if (opts->patch_mode)
+                       die(_("--pathspec-from-file is incompatible with --patch"));
+
+               parse_pathspec_file(&opts->pathspec, 0,
+                                   0,
+                                   prefix, opts->pathspec_from_file, opts->pathspec_file_nul);
+       } else if (opts->pathspec_file_nul) {
+               die(_("--pathspec-file-nul requires --pathspec-from-file"));
+       }
 
-               if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
+       if (opts->pathspec.nr) {
+               if (1 < !!opts->writeout_stage + !!opts->force + !!opts->merge)
                        die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
                              "checking out of the index."));
+       } else {
+               if (opts->accept_pathspec && !opts->empty_pathspec_ok &&
+                   !opts->patch_mode)  /* patch mode is special */
+                       die(_("you must specify path(s) to restore"));
        }
 
-       if (opts.new_branch) {
+       if (opts->new_branch) {
                struct strbuf buf = STRBUF_INIT;
 
-               if (opts.new_branch_force)
-                       opts.branch_exists = validate_branchname(opts.new_branch, &buf);
+               if (opts->new_branch_force)
+                       opts->branch_exists = validate_branchname(opts->new_branch, &buf);
                else
-                       opts.branch_exists =
-                               validate_new_branchname(opts.new_branch, &buf, 0);
+                       opts->branch_exists =
+                               validate_new_branchname(opts->new_branch, &buf, 0);
                strbuf_release(&buf);
        }
 
        UNLEAK(opts);
-       if (opts.patch_mode || opts.pathspec.nr)
-               return checkout_paths(&opts, new.name);
+       if (opts->patch_mode || opts->pathspec.nr)
+               return checkout_paths(opts, &new_branch_info);
        else
-               return checkout_branch(&opts, &new);
+               return checkout_branch(opts, &new_branch_info);
+}
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+       struct checkout_opts opts;
+       struct option *options;
+       struct option checkout_options[] = {
+               OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+                          N_("create and checkout a new branch")),
+               OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+                          N_("create/reset and checkout a branch")),
+               OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
+               OPT_BOOL(0, "guess", &opts.dwim_new_local_branch,
+                        N_("second guess 'git checkout <no-such-branch>' (default)")),
+               OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
+               OPT_END()
+       };
+       int ret;
+
+       memset(&opts, 0, sizeof(opts));
+       opts.dwim_new_local_branch = 1;
+       opts.switch_branch_doing_nothing_is_ok = 1;
+       opts.only_merge_on_switching_branches = 0;
+       opts.accept_ref = 1;
+       opts.accept_pathspec = 1;
+       opts.implicit_detach = 1;
+       opts.can_switch_when_in_progress = 1;
+       opts.orphan_from_empty_tree = 0;
+       opts.empty_pathspec_ok = 1;
+       opts.overlay_mode = -1;
+       opts.checkout_index = -2;    /* default on */
+       opts.checkout_worktree = -2; /* default on */
+
+       if (argc == 3 && !strcmp(argv[1], "-b")) {
+               /*
+                * User ran 'git checkout -b <branch>' and expects
+                * the same behavior as 'git switch -c <branch>'.
+                */
+               opts.switch_branch_doing_nothing_is_ok = 0;
+               opts.only_merge_on_switching_branches = 1;
+       }
+
+       options = parse_options_dup(checkout_options);
+       options = add_common_options(&opts, options);
+       options = add_common_switch_branch_options(&opts, options);
+       options = add_checkout_path_options(&opts, options);
+
+       ret = checkout_main(argc, argv, prefix, &opts,
+                           options, checkout_usage);
+       FREE_AND_NULL(options);
+       return ret;
+}
+
+int cmd_switch(int argc, const char **argv, const char *prefix)
+{
+       struct checkout_opts opts;
+       struct option *options = NULL;
+       struct option switch_options[] = {
+               OPT_STRING('c', "create", &opts.new_branch, N_("branch"),
+                          N_("create and switch to a new branch")),
+               OPT_STRING('C', "force-create", &opts.new_branch_force, N_("branch"),
+                          N_("create/reset and switch to a branch")),
+               OPT_BOOL(0, "guess", &opts.dwim_new_local_branch,
+                        N_("second guess 'git switch <no-such-branch>'")),
+               OPT_BOOL(0, "discard-changes", &opts.discard_changes,
+                        N_("throw away local modifications")),
+               OPT_END()
+       };
+       int ret;
+
+       memset(&opts, 0, sizeof(opts));
+       opts.dwim_new_local_branch = 1;
+       opts.accept_ref = 1;
+       opts.accept_pathspec = 0;
+       opts.switch_branch_doing_nothing_is_ok = 0;
+       opts.only_merge_on_switching_branches = 1;
+       opts.implicit_detach = 0;
+       opts.can_switch_when_in_progress = 0;
+       opts.orphan_from_empty_tree = 1;
+       opts.overlay_mode = -1;
+
+       options = parse_options_dup(switch_options);
+       options = add_common_options(&opts, options);
+       options = add_common_switch_branch_options(&opts, options);
+
+       cb_option = 'c';
+
+       ret = checkout_main(argc, argv, prefix, &opts,
+                           options, switch_branch_usage);
+       FREE_AND_NULL(options);
+       return ret;
+}
+
+int cmd_restore(int argc, const char **argv, const char *prefix)
+{
+       struct checkout_opts opts;
+       struct option *options;
+       struct option restore_options[] = {
+               OPT_STRING('s', "source", &opts.from_treeish, "<tree-ish>",
+                          N_("which tree-ish to checkout from")),
+               OPT_BOOL('S', "staged", &opts.checkout_index,
+                          N_("restore the index")),
+               OPT_BOOL('W', "worktree", &opts.checkout_worktree,
+                          N_("restore the working tree (default)")),
+               OPT_BOOL(0, "ignore-unmerged", &opts.ignore_unmerged,
+                        N_("ignore unmerged entries")),
+               OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode")),
+               OPT_END()
+       };
+       int ret;
+
+       memset(&opts, 0, sizeof(opts));
+       opts.accept_ref = 0;
+       opts.accept_pathspec = 1;
+       opts.empty_pathspec_ok = 0;
+       opts.overlay_mode = 0;
+       opts.checkout_index = -1;    /* default off */
+       opts.checkout_worktree = -2; /* default on */
+       opts.ignore_unmerged_opt = "--ignore-unmerged";
+
+       options = parse_options_dup(restore_options);
+       options = add_common_options(&opts, options);
+       options = add_checkout_path_options(&opts, options);
+
+       ret = checkout_main(argc, argv, prefix, &opts,
+                           options, restore_usage);
+       FREE_AND_NULL(options);
+       return ret;
 }