Imported Upstream version 2.23.3
[platform/upstream/git.git] / submodule.c
index 939d687..9da7181 100644 (file)
@@ -1,4 +1,3 @@
-#define NO_THE_INDEX_COMPATIBILITY_MACROS
 
 #include "cache.h"
 #include "repository.h"
@@ -22,9 +21,9 @@
 #include "worktree.h"
 #include "parse-options.h"
 #include "object-store.h"
+#include "commit-reach.h"
 
 static int config_update_recurse_submodules = RECURSE_SUBMODULES_OFF;
-static struct string_list changed_submodule_names = STRING_LIST_INIT_DUP;
 static int initialized_fetch_ref_tips;
 static struct oid_array ref_tips_before_fetch;
 static struct oid_array ref_tips_after_fetch;
@@ -51,6 +50,24 @@ int is_gitmodules_unmerged(const struct index_state *istate)
 }
 
 /*
+ * Check if the .gitmodules file is safe to write.
+ *
+ * Writing to the .gitmodules file requires that the file exists in the
+ * working tree or, if it doesn't, that a brand new .gitmodules file is going
+ * to be created (i.e. it's neither in the index nor in the current branch).
+ *
+ * It is not safe to write to .gitmodules if it's not in the working tree but
+ * it is in the index or in the current branch, because writing new values
+ * (and staging them) would blindly overwrite ALL the old content.
+ */
+int is_writing_gitmodules_ok(void)
+{
+       struct object_id oid;
+       return file_exists(GITMODULES_FILE) ||
+               (get_oid(GITMODULES_INDEX, &oid) < 0 && get_oid(GITMODULES_HEAD, &oid) < 0);
+}
+
+/*
  * Check if the .gitmodules file has unstaged modifications.  This must be
  * checked before allowing modifications to the .gitmodules file with the
  * intention to stage them later, because when continuing we would stage the
@@ -65,8 +82,7 @@ int is_staging_gitmodules_ok(struct index_state *istate)
        if ((pos >= 0) && (pos < istate->cache_nr)) {
                struct stat st;
                if (lstat(GITMODULES_FILE, &st) == 0 &&
-                   ie_match_stat(istate, istate->cache[pos], &st,
-                                 CE_MATCH_IGNORE_FSMONITOR) & DATA_CHANGED)
+                   ie_match_stat(istate, istate->cache[pos], &st, 0) & DATA_CHANGED)
                        return 0;
        }
 
@@ -89,11 +105,12 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 {
        struct strbuf entry = STRBUF_INIT;
        const struct submodule *submodule;
+       int ret;
 
        if (!file_exists(GITMODULES_FILE)) /* Do nothing without .gitmodules */
                return -1;
 
-       if (is_gitmodules_unmerged(&the_index))
+       if (is_gitmodules_unmerged(the_repository->index))
                die(_("Cannot change unmerged .gitmodules, resolve merge conflicts first"));
 
        submodule = submodule_from_path(the_repository, &null_oid, oldpath);
@@ -104,14 +121,9 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
        strbuf_addstr(&entry, "submodule.");
        strbuf_addstr(&entry, submodule->name);
        strbuf_addstr(&entry, ".path");
-       if (git_config_set_in_file_gently(GITMODULES_FILE, entry.buf, newpath) < 0) {
-               /* Maybe the user already did that, don't error out here */
-               warning(_("Could not update .gitmodules entry %s"), entry.buf);
-               strbuf_release(&entry);
-               return -1;
-       }
+       ret = config_set_in_gitmodules_file_gently(entry.buf, newpath);
        strbuf_release(&entry);
-       return 0;
+       return ret;
 }
 
 /*
@@ -127,7 +139,7 @@ int remove_path_from_gitmodules(const char *path)
        if (!file_exists(GITMODULES_FILE)) /* Do nothing without .gitmodules */
                return -1;
 
-       if (is_gitmodules_unmerged(&the_index))
+       if (is_gitmodules_unmerged(the_repository->index))
                die(_("Cannot change unmerged .gitmodules, resolve merge conflicts first"));
 
        submodule = submodule_from_path(the_repository, &null_oid, path);
@@ -188,7 +200,7 @@ void set_diffopt_flags_from_submodule_config(struct diff_options *diffopt,
 
                if (ignore)
                        handle_ignore_submodules_arg(diffopt, ignore);
-               else if (is_gitmodules_unmerged(&the_index))
+               else if (is_gitmodules_unmerged(the_repository->index))
                        diffopt->flags.ignore_submodules = 1;
        }
 }
@@ -258,7 +270,7 @@ int is_submodule_active(struct repository *repo, const char *path)
                }
 
                parse_pathspec(&ps, 0, 0, NULL, args.argv);
-               ret = match_pathspec(&ps, path, strlen(path), 0, NULL, 1);
+               ret = match_pathspec(repo->index, &ps, path, strlen(path), 0, NULL, 1);
 
                argv_array_clear(&args);
                clear_pathspec(&ps);
@@ -420,6 +432,10 @@ void handle_ignore_submodules_arg(struct diff_options *diffopt,
                diffopt->flags.ignore_dirty_submodules = 1;
        else if (strcmp(arg, "none"))
                die("bad --ignore-submodules argument: %s", arg);
+       /*
+        * Please update _git_status() in git-completion.bash when you
+        * add new options
+        */
 }
 
 static int prepare_submodule_summary(struct rev_info *rev, const char *path,
@@ -428,7 +444,7 @@ static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 {
        struct commit_list *list;
 
-       init_revisions(rev, NULL);
+       repo_init_revisions(the_repository, rev, NULL);
        setup_revisions(0, NULL, rev, NULL);
        rev->left_right = 1;
        rev->first_parent_only = 1;
@@ -443,7 +459,7 @@ static int prepare_submodule_summary(struct rev_info *rev, const char *path,
        return prepare_revision_walk(rev);
 }
 
-static void print_submodule_summary(struct rev_info *rev, struct diff_options *o)
+static void print_submodule_summary(struct repository *r, struct rev_info *rev, struct diff_options *o)
 {
        static const char format[] = "  %m %s";
        struct strbuf sb = STRBUF_INIT;
@@ -454,7 +470,8 @@ static void print_submodule_summary(struct rev_info *rev, struct diff_options *o
                ctx.date_mode = rev->date_mode;
                ctx.output_encoding = get_log_output_encoding();
                strbuf_setlen(&sb, 0);
-               format_commit_message(commit, format, &sb, &ctx);
+               repo_format_commit_message(r, commit, format, &sb,
+                                     &ctx);
                strbuf_addch(&sb, '\n');
                if (commit->object.flags & SYMMETRIC_LEFT)
                        diff_emit_submodule_del(o, sb.buf);
@@ -481,14 +498,52 @@ void prepare_submodule_repo_env(struct argv_array *out)
                         DEFAULT_GIT_DIR_ENVIRONMENT);
 }
 
-/* Helper function to display the submodule header line prior to the full
- * summary output. If it can locate the submodule objects directory it will
- * attempt to lookup both the left and right commits and put them into the
- * left and right pointers.
+static void prepare_submodule_repo_env_in_gitdir(struct argv_array *out)
+{
+       prepare_submodule_repo_env_no_git_dir(out);
+       argv_array_pushf(out, "%s=.", GIT_DIR_ENVIRONMENT);
+}
+
+/*
+ * Initialize a repository struct for a submodule based on the provided 'path'.
+ *
+ * Unlike repo_submodule_init, this tolerates submodules not present
+ * in .gitmodules. This function exists only to preserve historical behavior,
+ *
+ * Returns the repository struct on success,
+ * NULL when the submodule is not present.
  */
-static void show_submodule_header(struct diff_options *o, const char *path,
+static struct repository *open_submodule(const char *path)
+{
+       struct strbuf sb = STRBUF_INIT;
+       struct repository *out = xmalloc(sizeof(*out));
+
+       if (submodule_to_gitdir(&sb, path) || repo_init(out, sb.buf, NULL)) {
+               strbuf_release(&sb);
+               free(out);
+               return NULL;
+       }
+
+       /* Mark it as a submodule */
+       out->submodule_prefix = xstrdup(path);
+
+       strbuf_release(&sb);
+       return out;
+}
+
+/*
+ * Helper function to display the submodule header line prior to the full
+ * summary output.
+ *
+ * If it can locate the submodule git directory it will create a repository
+ * handle for the submodule and lookup both the left and right commits and
+ * put them into the left and right pointers.
+ */
+static void show_submodule_header(struct diff_options *o,
+               const char *path,
                struct object_id *one, struct object_id *two,
                unsigned dirty_submodule,
+               struct repository *sub,
                struct commit **left, struct commit **right,
                struct commit_list **merge_bases)
 {
@@ -507,7 +562,7 @@ static void show_submodule_header(struct diff_options *o, const char *path,
        else if (is_null_oid(two))
                message = "(submodule deleted)";
 
-       if (add_submodule_odb(path)) {
+       if (!sub) {
                if (!message)
                        message = "(commits not present)";
                goto output_header;
@@ -517,8 +572,8 @@ static void show_submodule_header(struct diff_options *o, const char *path,
         * Attempt to lookup the commit references, and determine if this is
         * a fast forward or fast backwards update.
         */
-       *left = lookup_commit_reference(one);
-       *right = lookup_commit_reference(two);
+       *left = lookup_commit_reference(sub, one);
+       *right = lookup_commit_reference(sub, two);
 
        /*
         * Warn about missing commits in the submodule project, but only if
@@ -528,7 +583,7 @@ static void show_submodule_header(struct diff_options *o, const char *path,
             (!is_null_oid(two) && !*right))
                message = "(commits not present)";
 
-       *merge_bases = get_merge_bases(*left, *right);
+       *merge_bases = repo_get_merge_bases(sub, *left, *right);
        if (*merge_bases) {
                if ((*merge_bases)->item == *left)
                        fast_forward = 1;
@@ -536,7 +591,7 @@ static void show_submodule_header(struct diff_options *o, const char *path,
                        fast_backward = 1;
        }
 
-       if (!oidcmp(one, two)) {
+       if (oideq(one, two)) {
                strbuf_release(&sb);
                return;
        }
@@ -562,16 +617,18 @@ void show_submodule_summary(struct diff_options *o, const char *path,
        struct rev_info rev;
        struct commit *left = NULL, *right = NULL;
        struct commit_list *merge_bases = NULL;
+       struct repository *sub;
 
+       sub = open_submodule(path);
        show_submodule_header(o, path, one, two, dirty_submodule,
-                             &left, &right, &merge_bases);
+                             sub, &left, &right, &merge_bases);
 
        /*
         * If we don't have both a left and a right pointer, there is no
         * reason to try and display a summary. The header line should contain
         * all the information the user needs.
         */
-       if (!left || !right)
+       if (!left || !right || !sub)
                goto out;
 
        /* Treat revision walker failure the same as missing commits */
@@ -580,13 +637,17 @@ void show_submodule_summary(struct diff_options *o, const char *path,
                goto out;
        }
 
-       print_submodule_summary(&rev, o);
+       print_submodule_summary(sub, &rev, o);
 
 out:
        if (merge_bases)
                free_commit_list(merge_bases);
        clear_commit_marks(left, ~0);
        clear_commit_marks(right, ~0);
+       if (sub) {
+               repo_clear(sub);
+               free(sub);
+       }
 }
 
 void show_submodule_inline_diff(struct diff_options *o, const char *path,
@@ -598,9 +659,11 @@ void show_submodule_inline_diff(struct diff_options *o, const char *path,
        struct commit_list *merge_bases = NULL;
        struct child_process cp = CHILD_PROCESS_INIT;
        struct strbuf sb = STRBUF_INIT;
+       struct repository *sub;
 
+       sub = open_submodule(path);
        show_submodule_header(o, path, one, two, dirty_submodule,
-                             &left, &right, &merge_bases);
+                             sub, &left, &right, &merge_bases);
 
        /* We need a valid left and right commit to display a difference */
        if (!(left || is_null_oid(one)) ||
@@ -661,6 +724,10 @@ done:
                clear_commit_marks(left, ~0);
        if (right)
                clear_commit_marks(right, ~0);
+       if (sub) {
+               repo_clear(sub);
+               free(sub);
+       }
 }
 
 int should_update_submodules(void)
@@ -694,6 +761,7 @@ static struct oid_array *submodule_commits(struct string_list *submodules,
 }
 
 struct collect_changed_submodules_cb_data {
+       struct repository *repo;
        struct string_list *changed;
        const struct object_id *commit_oid;
 };
@@ -733,19 +801,21 @@ static void collect_changed_submodules_cb(struct diff_queue_struct *q,
                if (!S_ISGITLINK(p->two->mode))
                        continue;
 
-               submodule = submodule_from_path(the_repository,
+               submodule = submodule_from_path(me->repo,
                                                commit_oid, p->two->path);
                if (submodule)
                        name = submodule->name;
                else {
                        name = default_name_or_path(p->two->path);
                        /* make sure name does not collide with existing one */
-                       submodule = submodule_from_name(the_repository, commit_oid, name);
+                       if (name)
+                               submodule = submodule_from_name(me->repo,
+                                                               commit_oid, name);
                        if (submodule) {
                                warning("Submodule in commit %s at path: "
                                        "'%s' collides with a submodule named "
                                        "the same. Skipping it.",
-                                       oid_to_hex(commit_oid), name);
+                                       oid_to_hex(commit_oid), p->two->path);
                                name = NULL;
                        }
                }
@@ -764,13 +834,14 @@ static void collect_changed_submodules_cb(struct diff_queue_struct *q,
  * have a corresponding 'struct oid_array' (in the 'util' field) which lists
  * what the submodule pointers were updated to during the change.
  */
-static void collect_changed_submodules(struct string_list *changed,
+static void collect_changed_submodules(struct repository *r,
+                                      struct string_list *changed,
                                       struct argv_array *argv)
 {
        struct rev_info rev;
        const struct commit *commit;
 
-       init_revisions(&rev, NULL);
+       repo_init_revisions(r, &rev, NULL);
        setup_revisions(argv->argc, argv->argv, &rev, NULL);
        if (prepare_revision_walk(&rev))
                die("revision walk setup failed");
@@ -778,10 +849,11 @@ static void collect_changed_submodules(struct string_list *changed,
        while ((commit = get_revision(&rev))) {
                struct rev_info diff_rev;
                struct collect_changed_submodules_cb_data data;
+               data.repo = r;
                data.changed = changed;
                data.commit_oid = &commit->object.oid;
 
-               init_revisions(&diff_rev, NULL);
+               repo_init_revisions(r, &diff_rev, NULL);
                diff_rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
                diff_rev.diffopt.format_callback = collect_changed_submodules_cb;
                diff_rev.diffopt.format_callback_data = &data;
@@ -813,6 +885,7 @@ static int append_oid_to_argv(const struct object_id *oid, void *data)
 }
 
 struct has_commit_data {
+       struct repository *repo;
        int result;
        const char *path;
 };
@@ -821,7 +894,7 @@ static int check_has_commit(const struct object_id *oid, void *data)
 {
        struct has_commit_data *cb = data;
 
-       enum object_type type = oid_object_info(the_repository, oid, NULL);
+       enum object_type type = oid_object_info(cb->repo, oid, NULL);
 
        switch (type) {
        case OBJ_COMMIT:
@@ -839,9 +912,11 @@ static int check_has_commit(const struct object_id *oid, void *data)
        }
 }
 
-static int submodule_has_commits(const char *path, struct oid_array *commits)
+static int submodule_has_commits(struct repository *r,
+                                const char *path,
+                                struct oid_array *commits)
 {
-       struct has_commit_data has_commit = { 1, path };
+       struct has_commit_data has_commit = { r, 1, path };
 
        /*
         * Perform a cheap, but incorrect check for the existence of 'commits'.
@@ -884,9 +959,11 @@ static int submodule_has_commits(const char *path, struct oid_array *commits)
        return has_commit.result;
 }
 
-static int submodule_needs_pushing(const char *path, struct oid_array *commits)
+static int submodule_needs_pushing(struct repository *r,
+                                  const char *path,
+                                  struct oid_array *commits)
 {
-       if (!submodule_has_commits(path, commits))
+       if (!submodule_has_commits(r, path, commits))
                /*
                 * NOTE: We do consider it safe to return "no" here. The
                 * correct answer would be "We do not know" instead of
@@ -917,7 +994,7 @@ static int submodule_needs_pushing(const char *path, struct oid_array *commits)
                if (start_command(&cp))
                        die("Could not run 'git rev-list <commits> --not --remotes -n 1' command in submodule %s",
                                        path);
-               if (strbuf_read(&buf, cp.out, 41))
+               if (strbuf_read(&buf, cp.out, the_hash_algo->hexsz + 1))
                        needs_pushing = 1;
                finish_command(&cp);
                close(cp.out);
@@ -928,8 +1005,10 @@ static int submodule_needs_pushing(const char *path, struct oid_array *commits)
        return 0;
 }
 
-int find_unpushed_submodules(struct oid_array *commits,
-               const char *remotes_name, struct string_list *needs_pushing)
+int find_unpushed_submodules(struct repository *r,
+                            struct oid_array *commits,
+                            const char *remotes_name,
+                            struct string_list *needs_pushing)
 {
        struct string_list submodules = STRING_LIST_INIT_DUP;
        struct string_list_item *name;
@@ -941,14 +1020,14 @@ int find_unpushed_submodules(struct oid_array *commits,
        argv_array_push(&argv, "--not");
        argv_array_pushf(&argv, "--remotes=%s", remotes_name);
 
-       collect_changed_submodules(&submodules, &argv);
+       collect_changed_submodules(r, &submodules, &argv);
 
        for_each_string_list_item(name, &submodules) {
                struct oid_array *commits = name->util;
                const struct submodule *submodule;
                const char *path = NULL;
 
-               submodule = submodule_from_name(the_repository, &null_oid, name->string);
+               submodule = submodule_from_name(r, &null_oid, name->string);
                if (submodule)
                        path = submodule->path;
                else
@@ -957,7 +1036,7 @@ int find_unpushed_submodules(struct oid_array *commits,
                if (!path)
                        continue;
 
-               if (submodule_needs_pushing(path, commits))
+               if (submodule_needs_pushing(r, path, commits))
                        string_list_insert(needs_pushing, path);
        }
 
@@ -973,9 +1052,6 @@ static int push_submodule(const char *path,
                          const struct string_list *push_options,
                          int dry_run)
 {
-       if (add_submodule_odb(path))
-               return 1;
-
        if (for_each_remote_ref_submodule(path, has_remote, NULL) > 0) {
                struct child_process cp = CHILD_PROCESS_INIT;
                argv_array_push(&cp.args, "push");
@@ -1042,7 +1118,8 @@ static void submodule_push_check(const char *path, const char *head,
                die("process for submodule '%s' failed", path);
 }
 
-int push_unpushed_submodules(struct oid_array *commits,
+int push_unpushed_submodules(struct repository *r,
+                            struct oid_array *commits,
                             const struct remote *remote,
                             const struct refspec *rs,
                             const struct string_list *push_options,
@@ -1051,7 +1128,8 @@ int push_unpushed_submodules(struct oid_array *commits,
        int i, ret = 1;
        struct string_list needs_pushing = STRING_LIST_INIT_DUP;
 
-       if (!find_unpushed_submodules(commits, remote->name, &needs_pushing))
+       if (!find_unpushed_submodules(r, commits,
+                                     remote->name, &needs_pushing))
                return 1;
 
        /*
@@ -1108,14 +1186,14 @@ void check_for_new_submodule_commits(struct object_id *oid)
        oid_array_append(&ref_tips_after_fetch, oid);
 }
 
-static void calculate_changed_submodule_paths(void)
+static void calculate_changed_submodule_paths(struct repository *r,
+               struct string_list *changed_submodule_names)
 {
        struct argv_array argv = ARGV_ARRAY_INIT;
-       struct string_list changed_submodules = STRING_LIST_INIT_DUP;
-       const struct string_list_item *name;
+       struct string_list_item *name;
 
        /* No need to check if there are no submodules configured */
-       if (!submodule_from_path(the_repository, NULL, NULL))
+       if (!submodule_from_path(r, NULL, NULL))
                return;
 
        argv_array_push(&argv, "--"); /* argv[0] program name */
@@ -1129,14 +1207,14 @@ static void calculate_changed_submodule_paths(void)
         * Collect all submodules (whether checked out or not) for which new
         * commits have been recorded upstream in "changed_submodule_names".
         */
-       collect_changed_submodules(&changed_submodules, &argv);
+       collect_changed_submodules(r, changed_submodule_names, &argv);
 
-       for_each_string_list_item(name, &changed_submodules) {
+       for_each_string_list_item(name, changed_submodule_names) {
                struct oid_array *commits = name->util;
                const struct submodule *submodule;
                const char *path = NULL;
 
-               submodule = submodule_from_name(the_repository, &null_oid, name->string);
+               submodule = submodule_from_name(r, &null_oid, name->string);
                if (submodule)
                        path = submodule->path;
                else
@@ -1145,18 +1223,22 @@ static void calculate_changed_submodule_paths(void)
                if (!path)
                        continue;
 
-               if (!submodule_has_commits(path, commits))
-                       string_list_append(&changed_submodule_names, name->string);
+               if (submodule_has_commits(r, path, commits)) {
+                       oid_array_clear(commits);
+                       *name->string = '\0';
+               }
        }
 
-       free_submodules_oids(&changed_submodules);
+       string_list_remove_empty_items(changed_submodule_names, 1);
+
        argv_array_clear(&argv);
        oid_array_clear(&ref_tips_before_fetch);
        oid_array_clear(&ref_tips_after_fetch);
        initialized_fetch_ref_tips = 0;
 }
 
-int submodule_touches_in_range(struct object_id *excl_oid,
+int submodule_touches_in_range(struct repository *r,
+                              struct object_id *excl_oid,
                               struct object_id *incl_oid)
 {
        struct string_list subs = STRING_LIST_INIT_DUP;
@@ -1164,7 +1246,7 @@ int submodule_touches_in_range(struct object_id *excl_oid,
        int ret;
 
        /* No need to check if there are no submodules configured */
-       if (!submodule_from_path(the_repository, NULL, NULL))
+       if (!submodule_from_path(r, NULL, NULL))
                return 0;
 
        argv_array_push(&args, "--"); /* args[0] program name */
@@ -1174,7 +1256,7 @@ int submodule_touches_in_range(struct object_id *excl_oid,
                argv_array_push(&args, oid_to_hex(excl_oid));
        }
 
-       collect_changed_submodules(&subs, &args);
+       collect_changed_submodules(r, &subs, &args);
        ret = subs.nr;
 
        argv_array_clear(&args);
@@ -1192,8 +1274,16 @@ struct submodule_parallel_fetch {
        int default_option;
        int quiet;
        int result;
+
+       struct string_list changed_submodule_names;
+
+       /* Pending fetches by OIDs */
+       struct fetch_task **oid_fetch_tasks;
+       int oid_fetch_tasks_nr, oid_fetch_tasks_alloc;
 };
-#define SPF_INIT {0, ARGV_ARRAY_INIT, NULL, NULL, 0, 0, 0, 0}
+#define SPF_INIT {0, ARGV_ARRAY_INIT, NULL, NULL, 0, 0, 0, 0, \
+                 STRING_LIST_INIT_DUP, \
+                 NULL, 0, 0}
 
 static int get_fetch_recurse_config(const struct submodule *submodule,
                                    struct submodule_parallel_fetch *spf)
@@ -1220,40 +1310,126 @@ static int get_fetch_recurse_config(const struct submodule *submodule,
        return spf->default_option;
 }
 
+/*
+ * Fetch in progress (if callback data) or
+ * pending (if in oid_fetch_tasks in struct submodule_parallel_fetch)
+ */
+struct fetch_task {
+       struct repository *repo;
+       const struct submodule *sub;
+       unsigned free_sub : 1; /* Do we need to free the submodule? */
+
+       struct oid_array *commits; /* Ensure these commits are fetched */
+};
+
+/**
+ * When a submodule is not defined in .gitmodules, we cannot access it
+ * via the regular submodule-config. Create a fake submodule, which we can
+ * work on.
+ */
+static const struct submodule *get_non_gitmodules_submodule(const char *path)
+{
+       struct submodule *ret = NULL;
+       const char *name = default_name_or_path(path);
+
+       if (!name)
+               return NULL;
+
+       ret = xmalloc(sizeof(*ret));
+       memset(ret, 0, sizeof(*ret));
+       ret->path = name;
+       ret->name = name;
+
+       return (const struct submodule *) ret;
+}
+
+static struct fetch_task *fetch_task_create(struct repository *r,
+                                           const char *path)
+{
+       struct fetch_task *task = xmalloc(sizeof(*task));
+       memset(task, 0, sizeof(*task));
+
+       task->sub = submodule_from_path(r, &null_oid, path);
+       if (!task->sub) {
+               /*
+                * No entry in .gitmodules? Technically not a submodule,
+                * but historically we supported repositories that happen to be
+                * in-place where a gitlink is. Keep supporting them.
+                */
+               task->sub = get_non_gitmodules_submodule(path);
+               if (!task->sub) {
+                       free(task);
+                       return NULL;
+               }
+
+               task->free_sub = 1;
+       }
+
+       return task;
+}
+
+static void fetch_task_release(struct fetch_task *p)
+{
+       if (p->free_sub)
+               free((void*)p->sub);
+       p->free_sub = 0;
+       p->sub = NULL;
+
+       if (p->repo)
+               repo_clear(p->repo);
+       FREE_AND_NULL(p->repo);
+}
+
+static struct repository *get_submodule_repo_for(struct repository *r,
+                                                const struct submodule *sub)
+{
+       struct repository *ret = xmalloc(sizeof(*ret));
+
+       if (repo_submodule_init(ret, r, sub)) {
+               /*
+                * No entry in .gitmodules? Technically not a submodule,
+                * but historically we supported repositories that happen to be
+                * in-place where a gitlink is. Keep supporting them.
+                */
+               struct strbuf gitdir = STRBUF_INIT;
+               strbuf_repo_worktree_path(&gitdir, r, "%s/.git", sub->path);
+               if (repo_init(ret, gitdir.buf, NULL)) {
+                       strbuf_release(&gitdir);
+                       free(ret);
+                       return NULL;
+               }
+               strbuf_release(&gitdir);
+       }
+
+       return ret;
+}
+
 static int get_next_submodule(struct child_process *cp,
                              struct strbuf *err, void *data, void **task_cb)
 {
-       int ret = 0;
        struct submodule_parallel_fetch *spf = data;
 
        for (; spf->count < spf->r->index->cache_nr; spf->count++) {
-               struct strbuf submodule_path = STRBUF_INIT;
-               struct strbuf submodule_git_dir = STRBUF_INIT;
-               struct strbuf submodule_prefix = STRBUF_INIT;
                const struct cache_entry *ce = spf->r->index->cache[spf->count];
-               const char *git_dir, *default_argv;
-               const struct submodule *submodule;
-               struct submodule default_submodule = SUBMODULE_INIT;
+               const char *default_argv;
+               struct fetch_task *task;
 
                if (!S_ISGITLINK(ce->ce_mode))
                        continue;
 
-               submodule = submodule_from_path(spf->r, &null_oid, ce->name);
-               if (!submodule) {
-                       const char *name = default_name_or_path(ce->name);
-                       if (name) {
-                               default_submodule.path = default_submodule.name = name;
-                               submodule = &default_submodule;
-                       }
-               }
+               task = fetch_task_create(spf->r, ce->name);
+               if (!task)
+                       continue;
 
-               switch (get_fetch_recurse_config(submodule, spf))
+               switch (get_fetch_recurse_config(task->sub, spf))
                {
                default:
                case RECURSE_SUBMODULES_DEFAULT:
                case RECURSE_SUBMODULES_ON_DEMAND:
-                       if (!submodule || !unsorted_string_list_lookup(&changed_submodule_names,
-                                                        submodule->name))
+                       if (!task->sub ||
+                           !string_list_lookup(
+                                       &spf->changed_submodule_names,
+                                       task->sub->name))
                                continue;
                        default_argv = "on-demand";
                        break;
@@ -1264,16 +1440,12 @@ static int get_next_submodule(struct child_process *cp,
                        continue;
                }
 
-               strbuf_repo_worktree_path(&submodule_path, spf->r, "%s", ce->name);
-               strbuf_addf(&submodule_git_dir, "%s/.git", submodule_path.buf);
-               strbuf_addf(&submodule_prefix, "%s%s/", spf->prefix, ce->name);
-               git_dir = read_gitfile(submodule_git_dir.buf);
-               if (!git_dir)
-                       git_dir = submodule_git_dir.buf;
-               if (is_directory(git_dir)) {
+               task->repo = get_submodule_repo_for(spf->r, task->sub);
+               if (task->repo) {
+                       struct strbuf submodule_prefix = STRBUF_INIT;
                        child_process_init(cp);
-                       cp->dir = strbuf_detach(&submodule_path, NULL);
-                       prepare_submodule_repo_env(&cp->env_array);
+                       cp->dir = task->repo->gitdir;
+                       prepare_submodule_repo_env_in_gitdir(&cp->env_array);
                        cp->git_cmd = 1;
                        if (!spf->quiet)
                                strbuf_addf(err, "Fetching submodule %s%s\n",
@@ -1282,17 +1454,66 @@ static int get_next_submodule(struct child_process *cp,
                        argv_array_pushv(&cp->args, spf->args.argv);
                        argv_array_push(&cp->args, default_argv);
                        argv_array_push(&cp->args, "--submodule-prefix");
+
+                       strbuf_addf(&submodule_prefix, "%s%s/",
+                                                      spf->prefix,
+                                                      task->sub->path);
                        argv_array_push(&cp->args, submodule_prefix.buf);
-                       ret = 1;
-               }
-               strbuf_release(&submodule_path);
-               strbuf_release(&submodule_git_dir);
-               strbuf_release(&submodule_prefix);
-               if (ret) {
+
                        spf->count++;
+                       *task_cb = task;
+
+                       strbuf_release(&submodule_prefix);
                        return 1;
+               } else {
+
+                       fetch_task_release(task);
+                       free(task);
+
+                       /*
+                        * An empty directory is normal,
+                        * the submodule is not initialized
+                        */
+                       if (S_ISGITLINK(ce->ce_mode) &&
+                           !is_empty_dir(ce->name)) {
+                               spf->result = 1;
+                               strbuf_addf(err,
+                                           _("Could not access submodule '%s'"),
+                                           ce->name);
+                       }
                }
        }
+
+       if (spf->oid_fetch_tasks_nr) {
+               struct fetch_task *task =
+                       spf->oid_fetch_tasks[spf->oid_fetch_tasks_nr - 1];
+               struct strbuf submodule_prefix = STRBUF_INIT;
+               spf->oid_fetch_tasks_nr--;
+
+               strbuf_addf(&submodule_prefix, "%s%s/",
+                           spf->prefix, task->sub->path);
+
+               child_process_init(cp);
+               prepare_submodule_repo_env_in_gitdir(&cp->env_array);
+               cp->git_cmd = 1;
+               cp->dir = task->repo->gitdir;
+
+               argv_array_init(&cp->args);
+               argv_array_pushv(&cp->args, spf->args.argv);
+               argv_array_push(&cp->args, "on-demand");
+               argv_array_push(&cp->args, "--submodule-prefix");
+               argv_array_push(&cp->args, submodule_prefix.buf);
+
+               /* NEEDSWORK: have get_default_remote from submodule--helper */
+               argv_array_push(&cp->args, "origin");
+               oid_array_for_each_unique(task->commits,
+                                         append_oid_to_argv, &cp->args);
+
+               *task_cb = task;
+               strbuf_release(&submodule_prefix);
+               return 1;
+       }
+
        return 0;
 }
 
@@ -1300,20 +1521,73 @@ static int fetch_start_failure(struct strbuf *err,
                               void *cb, void *task_cb)
 {
        struct submodule_parallel_fetch *spf = cb;
+       struct fetch_task *task = task_cb;
 
        spf->result = 1;
 
+       fetch_task_release(task);
        return 0;
 }
 
+static int commit_missing_in_sub(const struct object_id *oid, void *data)
+{
+       struct repository *subrepo = data;
+
+       enum object_type type = oid_object_info(subrepo, oid, NULL);
+
+       return type != OBJ_COMMIT;
+}
+
 static int fetch_finish(int retvalue, struct strbuf *err,
                        void *cb, void *task_cb)
 {
        struct submodule_parallel_fetch *spf = cb;
+       struct fetch_task *task = task_cb;
+
+       struct string_list_item *it;
+       struct oid_array *commits;
 
        if (retvalue)
+               /*
+                * NEEDSWORK: This indicates that the overall fetch
+                * failed, even though there may be a subsequent fetch
+                * by commit hash that might work. It may be a good
+                * idea to not indicate failure in this case, and only
+                * indicate failure if the subsequent fetch fails.
+                */
                spf->result = 1;
 
+       if (!task || !task->sub)
+               BUG("callback cookie bogus");
+
+       /* Is this the second time we process this submodule? */
+       if (task->commits)
+               goto out;
+
+       it = string_list_lookup(&spf->changed_submodule_names, task->sub->name);
+       if (!it)
+               /* Could be an unchanged submodule, not contained in the list */
+               goto out;
+
+       commits = it->util;
+       oid_array_filter(commits,
+                        commit_missing_in_sub,
+                        task->repo);
+
+       /* Are there commits we want, but do not exist? */
+       if (commits->nr) {
+               task->commits = commits;
+               ALLOC_GROW(spf->oid_fetch_tasks,
+                          spf->oid_fetch_tasks_nr + 1,
+                          spf->oid_fetch_tasks_alloc);
+               spf->oid_fetch_tasks[spf->oid_fetch_tasks_nr] = task;
+               spf->oid_fetch_tasks_nr++;
+               return 0;
+       }
+
+out:
+       fetch_task_release(task);
+
        return 0;
 }
 
@@ -1344,16 +1618,18 @@ int fetch_populated_submodules(struct repository *r,
        argv_array_push(&spf.args, "--recurse-submodules-default");
        /* default value, "--submodule-prefix" and its value are added later */
 
-       calculate_changed_submodule_paths();
-       run_processes_parallel(max_parallel_jobs,
-                              get_next_submodule,
-                              fetch_start_failure,
-                              fetch_finish,
-                              &spf);
+       calculate_changed_submodule_paths(r, &spf.changed_submodule_names);
+       string_list_sort(&spf.changed_submodule_names);
+       run_processes_parallel_tr2(max_parallel_jobs,
+                                  get_next_submodule,
+                                  fetch_start_failure,
+                                  fetch_finish,
+                                  &spf,
+                                  "submodule", "parallel/fetch");
 
        argv_array_clear(&spf.args);
 out:
-       string_list_clear(&changed_submodule_names, 1);
+       free_submodules_oids(&spf.changed_submodule_names);
        return spf.result;
 }
 
@@ -1532,6 +1808,18 @@ out:
        return ret;
 }
 
+void submodule_unset_core_worktree(const struct submodule *sub)
+{
+       char *config_path = xstrfmt("%s/modules/%s/config",
+                                   get_git_common_dir(), sub->name);
+
+       if (git_config_set_in_file_gently(config_path, "core.worktree", NULL))
+               warning(_("Could not unset core.worktree setting in submodule '%s'"),
+                         sub->path);
+
+       free(config_path);
+}
+
 static const char *get_super_prefix_or_empty(void)
 {
        const char *s = get_super_prefix();
@@ -1622,7 +1910,7 @@ int submodule_move_head(const char *path,
        if (!(flags & SUBMODULE_MOVE_HEAD_DRY_RUN)) {
                if (old_head) {
                        if (!submodule_uses_gitfile(path))
-                               absorb_git_dir_into_superproject("", path,
+                               absorb_git_dir_into_superproject(path,
                                        ABSORB_GITDIR_RECURSE_SUBMODULES);
                } else {
                        char *gitdir = xstrfmt("%s/modules/%s",
@@ -1668,7 +1956,7 @@ int submodule_move_head(const char *path,
        argv_array_push(&cp.args, new_head ? new_head : empty_tree_oid_hex());
 
        if (run_command(&cp)) {
-               ret = -1;
+               ret = error(_("Submodule '%s' could not be updated."), path);
                goto out;
        }
 
@@ -1697,21 +1985,63 @@ int submodule_move_head(const char *path,
 
                        if (is_empty_dir(path))
                                rmdir_or_warn(path);
+
+                       submodule_unset_core_worktree(sub);
                }
        }
 out:
        return ret;
 }
 
+int validate_submodule_git_dir(char *git_dir, const char *submodule_name)
+{
+       size_t len = strlen(git_dir), suffix_len = strlen(submodule_name);
+       char *p;
+       int ret = 0;
+
+       if (len <= suffix_len || (p = git_dir + len - suffix_len)[-1] != '/' ||
+           strcmp(p, submodule_name))
+               BUG("submodule name '%s' not a suffix of git dir '%s'",
+                   submodule_name, git_dir);
+
+       /*
+        * We prevent the contents of sibling submodules' git directories to
+        * clash.
+        *
+        * Example: having a submodule named `hippo` and another one named
+        * `hippo/hooks` would result in the git directories
+        * `.git/modules/hippo/` and `.git/modules/hippo/hooks/`, respectively,
+        * but the latter directory is already designated to contain the hooks
+        * of the former.
+        */
+       for (; *p; p++) {
+               if (is_dir_sep(*p)) {
+                       char c = *p;
+
+                       *p = '\0';
+                       if (is_git_directory(git_dir))
+                               ret = -1;
+                       *p = c;
+
+                       if (ret < 0)
+                               return error(_("submodule git dir '%s' is "
+                                              "inside git dir '%.*s'"),
+                                            git_dir,
+                                            (int)(p - git_dir), git_dir);
+               }
+       }
+
+       return 0;
+}
+
 /*
  * Embeds a single submodules git directory into the superprojects git dir,
  * non recursively.
  */
-static void relocate_single_git_dir_into_superproject(const char *prefix,
-                                                     const char *path)
+static void relocate_single_git_dir_into_superproject(const char *path)
 {
        char *old_git_dir = NULL, *real_old_git_dir = NULL, *real_new_git_dir = NULL;
-       const char *new_git_dir;
+       char *new_git_dir;
        const struct submodule *sub;
 
        if (submodule_uses_worktrees(path))
@@ -1729,10 +2059,14 @@ static void relocate_single_git_dir_into_superproject(const char *prefix,
        if (!sub)
                die(_("could not lookup name for submodule '%s'"), path);
 
-       new_git_dir = git_path("modules/%s", sub->name);
+       new_git_dir = git_pathdup("modules/%s", sub->name);
+       if (validate_submodule_git_dir(new_git_dir, sub->name) < 0)
+               die(_("refusing to move '%s' into an existing git dir"),
+                   real_old_git_dir);
        if (safe_create_leading_directories_const(new_git_dir) < 0)
                die(_("could not create directory '%s'"), new_git_dir);
        real_new_git_dir = real_pathdup(new_git_dir, 1);
+       free(new_git_dir);
 
        fprintf(stderr, _("Migrating git directory of '%s%s' from\n'%s' to\n'%s'\n"),
                get_super_prefix_or_empty(), path,
@@ -1750,8 +2084,7 @@ static void relocate_single_git_dir_into_superproject(const char *prefix,
  * having its git directory within the working tree to the git dir nested
  * in its superprojects git dir under modules/.
  */
-void absorb_git_dir_into_superproject(const char *prefix,
-                                     const char *path,
+void absorb_git_dir_into_superproject(const char *path,
                                      unsigned flags)
 {
        int err_code;
@@ -1792,7 +2125,7 @@ void absorb_git_dir_into_superproject(const char *prefix,
                char *real_common_git_dir = real_pathdup(get_git_common_dir(), 1);
 
                if (!starts_with(real_sub_git_dir, real_common_git_dir))
-                       relocate_single_git_dir_into_superproject(prefix, path);
+                       relocate_single_git_dir_into_superproject(path);
 
                free(real_sub_git_dir);
                free(real_common_git_dir);
@@ -1878,7 +2211,7 @@ const char *get_superproject_working_tree(void)
                 * We're only interested in the name after the tab.
                 */
                super_sub = strchr(sb.buf, '\t') + 1;
-               super_sub_len = sb.buf + sb.len - super_sub - 1;
+               super_sub_len = strlen(super_sub);
 
                if (super_sub_len > cwd_len ||
                    strcmp(&cwd[cwd_len - super_sub_len], super_sub))