Imported Upstream version 2.20.1
[platform/upstream/git.git] / commit.c
index 4b39c19..d13a7bc 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -1,81 +1,83 @@
 #include "cache.h"
 #include "tag.h"
 #include "commit.h"
+#include "commit-graph.h"
+#include "repository.h"
+#include "object-store.h"
 #include "pkt-line.h"
 #include "utf8.h"
 #include "diff.h"
 #include "revision.h"
 #include "notes.h"
+#include "alloc.h"
 #include "gpg-interface.h"
+#include "mergesort.h"
+#include "commit-slab.h"
+#include "prio-queue.h"
+#include "sha1-lookup.h"
+#include "wt-status.h"
+#include "advice.h"
+#include "refs.h"
+#include "commit-reach.h"
+
+static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
 
 int save_commit_buffer = 1;
 
 const char *commit_type = "commit";
 
-static struct commit *check_commit(struct object *obj,
-                                  const unsigned char *sha1,
-                                  int quiet)
-{
-       if (obj->type != OBJ_COMMIT) {
-               if (!quiet)
-                       error("Object %s is a %s, not a commit",
-                             sha1_to_hex(sha1), typename(obj->type));
-               return NULL;
-       }
-       return (struct commit *) obj;
-}
-
-struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
-                                             int quiet)
+struct commit *lookup_commit_reference_gently(struct repository *r,
+               const struct object_id *oid, int quiet)
 {
-       struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
+       struct object *obj = deref_tag(r,
+                                      parse_object(r, oid),
+                                      NULL, 0);
 
        if (!obj)
                return NULL;
-       return check_commit(obj, sha1, quiet);
+       return object_as_type(r, obj, OBJ_COMMIT, quiet);
 }
 
-struct commit *lookup_commit_reference(const unsigned char *sha1)
+struct commit *lookup_commit_reference(struct repository *r, const struct object_id *oid)
 {
-       return lookup_commit_reference_gently(sha1, 0);
+       return lookup_commit_reference_gently(r, oid, 0);
 }
 
-struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name)
+struct commit *lookup_commit_or_die(const struct object_id *oid, const char *ref_name)
 {
-       struct commit *c = lookup_commit_reference(sha1);
+       struct commit *c = lookup_commit_reference(the_repository, oid);
        if (!c)
                die(_("could not parse %s"), ref_name);
-       if (hashcmp(sha1, c->object.sha1)) {
+       if (!oideq(oid, &c->object.oid)) {
                warning(_("%s %s is not a commit!"),
-                       ref_name, sha1_to_hex(sha1));
+                       ref_name, oid_to_hex(oid));
        }
        return c;
 }
 
-struct commit *lookup_commit(const unsigned char *sha1)
+struct commit *lookup_commit(struct repository *r, const struct object_id *oid)
 {
-       struct object *obj = lookup_object(sha1);
+       struct object *obj = lookup_object(r, oid->hash);
        if (!obj)
-               return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
-       if (!obj->type)
-               obj->type = OBJ_COMMIT;
-       return check_commit(obj, sha1, 0);
+               return create_object(r, oid->hash,
+                                    alloc_commit_node(r));
+       return object_as_type(r, obj, OBJ_COMMIT, 0);
 }
 
 struct commit *lookup_commit_reference_by_name(const char *name)
 {
-       unsigned char sha1[20];
+       struct object_id oid;
        struct commit *commit;
 
-       if (get_sha1(name, sha1))
+       if (get_oid_committish(name, &oid))
                return NULL;
-       commit = lookup_commit_reference(sha1);
-       if (!commit || parse_commit(commit))
+       commit = lookup_commit_reference(the_repository, &oid);
+       if (parse_commit(commit))
                return NULL;
        return commit;
 }
 
-static unsigned long parse_commit_date(const char *buf, const char *tail)
+static timestamp_t parse_commit_date(const char *buf, const char *tail)
 {
        const char *dateptr;
 
@@ -98,193 +100,329 @@ static unsigned long parse_commit_date(const char *buf, const char *tail)
                /* nada */;
        if (buf >= tail)
                return 0;
-       /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
-       return strtoul(dateptr, NULL, 10);
-}
-
-static struct commit_graft **commit_graft;
-static int commit_graft_alloc, commit_graft_nr;
-
-static int commit_graft_pos(const unsigned char *sha1)
-{
-       int lo, hi;
-       lo = 0;
-       hi = commit_graft_nr;
-       while (lo < hi) {
-               int mi = (lo + hi) / 2;
-               struct commit_graft *graft = commit_graft[mi];
-               int cmp = hashcmp(sha1, graft->sha1);
-               if (!cmp)
-                       return mi;
-               if (cmp < 0)
-                       hi = mi;
-               else
-                       lo = mi + 1;
-       }
-       return -lo - 1;
+       /* dateptr < buf && buf[-1] == '\n', so parsing will stop at buf-1 */
+       return parse_timestamp(dateptr, NULL, 10);
+}
+
+static const unsigned char *commit_graft_sha1_access(size_t index, void *table)
+{
+       struct commit_graft **commit_graft_table = table;
+       return commit_graft_table[index]->oid.hash;
 }
 
-int register_commit_graft(struct commit_graft *graft, int ignore_dups)
+static int commit_graft_pos(struct repository *r, const unsigned char *sha1)
 {
-       int pos = commit_graft_pos(graft->sha1);
+       return sha1_pos(sha1, r->parsed_objects->grafts,
+                       r->parsed_objects->grafts_nr,
+                       commit_graft_sha1_access);
+}
+
+int register_commit_graft(struct repository *r, struct commit_graft *graft,
+                         int ignore_dups)
+{
+       int pos = commit_graft_pos(r, graft->oid.hash);
 
        if (0 <= pos) {
                if (ignore_dups)
                        free(graft);
                else {
-                       free(commit_graft[pos]);
-                       commit_graft[pos] = graft;
+                       free(r->parsed_objects->grafts[pos]);
+                       r->parsed_objects->grafts[pos] = graft;
                }
                return 1;
        }
        pos = -pos - 1;
-       if (commit_graft_alloc <= ++commit_graft_nr) {
-               commit_graft_alloc = alloc_nr(commit_graft_alloc);
-               commit_graft = xrealloc(commit_graft,
-                                       sizeof(*commit_graft) *
-                                       commit_graft_alloc);
-       }
-       if (pos < commit_graft_nr)
-               memmove(commit_graft + pos + 1,
-                       commit_graft + pos,
-                       (commit_graft_nr - pos - 1) *
-                       sizeof(*commit_graft));
-       commit_graft[pos] = graft;
+       ALLOC_GROW(r->parsed_objects->grafts,
+                  r->parsed_objects->grafts_nr + 1,
+                  r->parsed_objects->grafts_alloc);
+       r->parsed_objects->grafts_nr++;
+       if (pos < r->parsed_objects->grafts_nr)
+               memmove(r->parsed_objects->grafts + pos + 1,
+                       r->parsed_objects->grafts + pos,
+                       (r->parsed_objects->grafts_nr - pos - 1) *
+                       sizeof(*r->parsed_objects->grafts));
+       r->parsed_objects->grafts[pos] = graft;
        return 0;
 }
 
-struct commit_graft *read_graft_line(char *buf, int len)
+struct commit_graft *read_graft_line(struct strbuf *line)
 {
        /* The format is just "Commit Parent1 Parent2 ...\n" */
-       int i;
+       int i, phase;
+       const char *tail = NULL;
        struct commit_graft *graft = NULL;
+       struct object_id dummy_oid, *oid;
 
-       while (len && isspace(buf[len-1]))
-               buf[--len] = '\0';
-       if (buf[0] == '#' || buf[0] == '\0')
+       strbuf_rtrim(line);
+       if (!line->len || line->buf[0] == '#')
                return NULL;
-       if ((len + 1) % 41)
-               goto bad_graft_data;
-       i = (len + 1) / 41 - 1;
-       graft = xmalloc(sizeof(*graft) + 20 * i);
-       graft->nr_parent = i;
-       if (get_sha1_hex(buf, graft->sha1))
-               goto bad_graft_data;
-       for (i = 40; i < len; i += 41) {
-               if (buf[i] != ' ')
-                       goto bad_graft_data;
-               if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
+       /*
+        * phase 0 verifies line, counts hashes in line and allocates graft
+        * phase 1 fills graft
+        */
+       for (phase = 0; phase < 2; phase++) {
+               oid = graft ? &graft->oid : &dummy_oid;
+               if (parse_oid_hex(line->buf, oid, &tail))
                        goto bad_graft_data;
+               for (i = 0; *tail != '\0'; i++) {
+                       oid = graft ? &graft->parent[i] : &dummy_oid;
+                       if (!isspace(*tail++) || parse_oid_hex(tail, oid, &tail))
+                               goto bad_graft_data;
+               }
+               if (!graft) {
+                       graft = xmalloc(st_add(sizeof(*graft),
+                                              st_mult(sizeof(struct object_id), i)));
+                       graft->nr_parent = i;
+               }
        }
        return graft;
 
 bad_graft_data:
-       error("bad graft data: %s", buf);
-       free(graft);
+       error("bad graft data: %s", line->buf);
+       assert(!graft);
        return NULL;
 }
 
-static int read_graft_file(const char *graft_file)
+static int read_graft_file(struct repository *r, const char *graft_file)
 {
-       FILE *fp = fopen(graft_file, "r");
-       char buf[1024];
+       FILE *fp = fopen_or_warn(graft_file, "r");
+       struct strbuf buf = STRBUF_INIT;
        if (!fp)
                return -1;
-       while (fgets(buf, sizeof(buf), fp)) {
+       if (advice_graft_file_deprecated)
+               advise(_("Support for <GIT_DIR>/info/grafts is deprecated\n"
+                        "and will be removed in a future Git version.\n"
+                        "\n"
+                        "Please use \"git replace --convert-graft-file\"\n"
+                        "to convert the grafts into replace refs.\n"
+                        "\n"
+                        "Turn this message off by running\n"
+                        "\"git config advice.graftFileDeprecated false\""));
+       while (!strbuf_getwholeline(&buf, fp, '\n')) {
                /* The format is just "Commit Parent1 Parent2 ...\n" */
-               int len = strlen(buf);
-               struct commit_graft *graft = read_graft_line(buf, len);
+               struct commit_graft *graft = read_graft_line(&buf);
                if (!graft)
                        continue;
-               if (register_commit_graft(graft, 1))
-                       error("duplicate graft data: %s", buf);
+               if (register_commit_graft(r, graft, 1))
+                       error("duplicate graft data: %s", buf.buf);
        }
        fclose(fp);
+       strbuf_release(&buf);
        return 0;
 }
 
-static void prepare_commit_graft(void)
+void prepare_commit_graft(struct repository *r)
 {
-       static int commit_graft_prepared;
        char *graft_file;
 
-       if (commit_graft_prepared)
+       if (r->parsed_objects->commit_graft_prepared)
                return;
-       graft_file = get_graft_file();
-       read_graft_file(graft_file);
+       if (!startup_info->have_repository)
+               return;
+
+       graft_file = get_graft_file(r);
+       read_graft_file(r, graft_file);
        /* make sure shallows are read */
-       is_repository_shallow();
-       commit_graft_prepared = 1;
+       is_repository_shallow(r);
+       r->parsed_objects->commit_graft_prepared = 1;
 }
 
-struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
+struct commit_graft *lookup_commit_graft(struct repository *r, const struct object_id *oid)
 {
        int pos;
-       prepare_commit_graft();
-       pos = commit_graft_pos(sha1);
+       prepare_commit_graft(r);
+       pos = commit_graft_pos(r, oid->hash);
        if (pos < 0)
                return NULL;
-       return commit_graft[pos];
+       return r->parsed_objects->grafts[pos];
 }
 
 int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 {
        int i, ret;
-       for (i = ret = 0; i < commit_graft_nr && !ret; i++)
-               ret = fn(commit_graft[i], cb_data);
+       for (i = ret = 0; i < the_repository->parsed_objects->grafts_nr && !ret; i++)
+               ret = fn(the_repository->parsed_objects->grafts[i], cb_data);
        return ret;
 }
 
-int unregister_shallow(const unsigned char *sha1)
+int unregister_shallow(const struct object_id *oid)
 {
-       int pos = commit_graft_pos(sha1);
+       int pos = commit_graft_pos(the_repository, oid->hash);
        if (pos < 0)
                return -1;
-       if (pos + 1 < commit_graft_nr)
-               memmove(commit_graft + pos, commit_graft + pos + 1,
-                               sizeof(struct commit_graft *)
-                               * (commit_graft_nr - pos - 1));
-       commit_graft_nr--;
+       if (pos + 1 < the_repository->parsed_objects->grafts_nr)
+               MOVE_ARRAY(the_repository->parsed_objects->grafts + pos,
+                          the_repository->parsed_objects->grafts + pos + 1,
+                          the_repository->parsed_objects->grafts_nr - pos - 1);
+       the_repository->parsed_objects->grafts_nr--;
        return 0;
 }
 
-int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size)
+struct commit_buffer {
+       void *buffer;
+       unsigned long size;
+};
+define_commit_slab(buffer_slab, struct commit_buffer);
+
+struct buffer_slab *allocate_commit_buffer_slab(void)
+{
+       struct buffer_slab *bs = xmalloc(sizeof(*bs));
+       init_buffer_slab(bs);
+       return bs;
+}
+
+void free_commit_buffer_slab(struct buffer_slab *bs)
+{
+       clear_buffer_slab(bs);
+       free(bs);
+}
+
+void set_commit_buffer(struct repository *r, struct commit *commit, void *buffer, unsigned long size)
+{
+       struct commit_buffer *v = buffer_slab_at(
+               r->parsed_objects->buffer_slab, commit);
+       v->buffer = buffer;
+       v->size = size;
+}
+
+const void *get_cached_commit_buffer(struct repository *r, const struct commit *commit, unsigned long *sizep)
+{
+       struct commit_buffer *v = buffer_slab_peek(
+               r->parsed_objects->buffer_slab, commit);
+       if (!v) {
+               if (sizep)
+                       *sizep = 0;
+               return NULL;
+       }
+       if (sizep)
+               *sizep = v->size;
+       return v->buffer;
+}
+
+const void *get_commit_buffer(const struct commit *commit, unsigned long *sizep)
+{
+       const void *ret = get_cached_commit_buffer(the_repository, commit, sizep);
+       if (!ret) {
+               enum object_type type;
+               unsigned long size;
+               ret = read_object_file(&commit->object.oid, &type, &size);
+               if (!ret)
+                       die("cannot read commit object %s",
+                           oid_to_hex(&commit->object.oid));
+               if (type != OBJ_COMMIT)
+                       die("expected commit for %s, got %s",
+                           oid_to_hex(&commit->object.oid), type_name(type));
+               if (sizep)
+                       *sizep = size;
+       }
+       return ret;
+}
+
+void unuse_commit_buffer(const struct commit *commit, const void *buffer)
+{
+       struct commit_buffer *v = buffer_slab_peek(
+               the_repository->parsed_objects->buffer_slab, commit);
+       if (!(v && v->buffer == buffer))
+               free((void *)buffer);
+}
+
+void free_commit_buffer(struct commit *commit)
+{
+       struct commit_buffer *v = buffer_slab_peek(
+               the_repository->parsed_objects->buffer_slab, commit);
+       if (v) {
+               FREE_AND_NULL(v->buffer);
+               v->size = 0;
+       }
+}
+
+struct tree *get_commit_tree(const struct commit *commit)
+{
+       if (commit->maybe_tree || !commit->object.parsed)
+               return commit->maybe_tree;
+
+       if (commit->graph_pos == COMMIT_NOT_FROM_GRAPH)
+               BUG("commit has NULL tree, but was not loaded from commit-graph");
+
+       return get_commit_tree_in_graph(the_repository, commit);
+}
+
+struct object_id *get_commit_tree_oid(const struct commit *commit)
+{
+       return &get_commit_tree(commit)->object.oid;
+}
+
+void release_commit_memory(struct commit *c)
+{
+       c->maybe_tree = NULL;
+       c->index = 0;
+       free_commit_buffer(c);
+       free_commit_list(c->parents);
+       /* TODO: what about commit->util? */
+
+       c->object.parsed = 0;
+}
+
+const void *detach_commit_buffer(struct commit *commit, unsigned long *sizep)
+{
+       struct commit_buffer *v = buffer_slab_peek(
+               the_repository->parsed_objects->buffer_slab, commit);
+       void *ret;
+
+       if (!v) {
+               if (sizep)
+                       *sizep = 0;
+               return NULL;
+       }
+       ret = v->buffer;
+       if (sizep)
+               *sizep = v->size;
+
+       v->buffer = NULL;
+       v->size = 0;
+       return ret;
+}
+
+int parse_commit_buffer(struct repository *r, struct commit *item, const void *buffer, unsigned long size, int check_graph)
 {
        const char *tail = buffer;
        const char *bufptr = buffer;
-       unsigned char parent[20];
+       struct object_id parent;
        struct commit_list **pptr;
        struct commit_graft *graft;
+       const int tree_entry_len = the_hash_algo->hexsz + 5;
+       const int parent_entry_len = the_hash_algo->hexsz + 7;
 
        if (item->object.parsed)
                return 0;
        item->object.parsed = 1;
        tail += size;
-       if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
-               return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
-       if (get_sha1_hex(bufptr + 5, parent) < 0)
+       if (tail <= bufptr + tree_entry_len + 1 || memcmp(bufptr, "tree ", 5) ||
+                       bufptr[tree_entry_len] != '\n')
+               return error("bogus commit object %s", oid_to_hex(&item->object.oid));
+       if (get_oid_hex(bufptr + 5, &parent) < 0)
                return error("bad tree pointer in commit %s",
-                            sha1_to_hex(item->object.sha1));
-       item->tree = lookup_tree(parent);
-       bufptr += 46; /* "tree " + "hex sha1" + "\n" */
+                            oid_to_hex(&item->object.oid));
+       item->maybe_tree = lookup_tree(r, &parent);
+       bufptr += tree_entry_len + 1; /* "tree " + "hex sha1" + "\n" */
        pptr = &item->parents;
 
-       graft = lookup_commit_graft(item->object.sha1);
-       while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
+       graft = lookup_commit_graft(r, &item->object.oid);
+       while (bufptr + parent_entry_len < tail && !memcmp(bufptr, "parent ", 7)) {
                struct commit *new_parent;
 
-               if (tail <= bufptr + 48 ||
-                   get_sha1_hex(bufptr + 7, parent) ||
-                   bufptr[47] != '\n')
-                       return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
-               bufptr += 48;
+               if (tail <= bufptr + parent_entry_len + 1 ||
+                   get_oid_hex(bufptr + 7, &parent) ||
+                   bufptr[parent_entry_len] != '\n')
+                       return error("bad parents in commit %s", oid_to_hex(&item->object.oid));
+               bufptr += parent_entry_len + 1;
                /*
                 * The clone is shallow if nr_parent < 0, and we must
                 * not traverse its real parents even when we unhide them.
                 */
                if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
                        continue;
-               new_parent = lookup_commit(parent);
+               new_parent = lookup_commit(r, &parent);
                if (new_parent)
                        pptr = &commit_list_insert(new_parent, pptr)->next;
        }
@@ -292,7 +430,8 @@ int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long s
                int i;
                struct commit *new_parent;
                for (i = 0; i < graft->nr_parent; i++) {
-                       new_parent = lookup_commit(graft->parent[i]);
+                       new_parent = lookup_commit(r,
+                                                  &graft->parent[i]);
                        if (!new_parent)
                                continue;
                        pptr = &commit_list_insert(new_parent, pptr)->next;
@@ -300,10 +439,13 @@ int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long s
        }
        item->date = parse_commit_date(bufptr, tail);
 
+       if (check_graph)
+               load_commit_graph_info(the_repository, item);
+
        return 0;
 }
 
-int parse_commit(struct commit *item)
+int parse_commit_internal(struct commit *item, int quiet_on_missing, int use_commit_graph)
 {
        enum object_type type;
        void *buffer;
@@ -314,24 +456,40 @@ int parse_commit(struct commit *item)
                return -1;
        if (item->object.parsed)
                return 0;
-       buffer = read_sha1_file(item->object.sha1, &type, &size);
+       if (use_commit_graph && parse_commit_in_graph(the_repository, item))
+               return 0;
+       buffer = read_object_file(&item->object.oid, &type, &size);
        if (!buffer)
-               return error("Could not read %s",
-                            sha1_to_hex(item->object.sha1));
+               return quiet_on_missing ? -1 :
+                       error("Could not read %s",
+                            oid_to_hex(&item->object.oid));
        if (type != OBJ_COMMIT) {
                free(buffer);
                return error("Object %s not a commit",
-                            sha1_to_hex(item->object.sha1));
+                            oid_to_hex(&item->object.oid));
        }
-       ret = parse_commit_buffer(item, buffer, size);
+
+       ret = parse_commit_buffer(the_repository, item, buffer, size, 0);
        if (save_commit_buffer && !ret) {
-               item->buffer = buffer;
+               set_commit_buffer(the_repository, item, buffer, size);
                return 0;
        }
        free(buffer);
        return ret;
 }
 
+int parse_commit_gently(struct commit *item, int quiet_on_missing)
+{
+       return parse_commit_internal(item, quiet_on_missing, 1);
+}
+
+void parse_commit_or_die(struct commit *item)
+{
+       if (parse_commit(item))
+               die("unable to parse commit %s",
+                   item ? oid_to_hex(&item->object.oid) : "(null)");
+}
+
 int find_commit_subject(const char *commit_buffer, const char **subject)
 {
        const char *eol;
@@ -340,9 +498,8 @@ int find_commit_subject(const char *commit_buffer, const char **subject)
        while (*p && (*p != '\n' || p[1] != '\n'))
                p++;
        if (*p) {
-               p += 2;
-               for (eol = p; *eol && *eol != '\n'; eol++)
-                       ; /* do nothing */
+               p = skip_blank_lines(p + 2);
+               eol = strchrnul(p, '\n');
        } else
                eol = p;
 
@@ -368,13 +525,21 @@ unsigned commit_list_count(const struct commit_list *l)
        return c;
 }
 
-void free_commit_list(struct commit_list *list)
+struct commit_list *copy_commit_list(struct commit_list *list)
 {
+       struct commit_list *head = NULL;
+       struct commit_list **pp = &head;
        while (list) {
-               struct commit_list *temp = list;
-               list = temp->next;
-               free(temp);
+               pp = commit_list_append(list->item, pp);
+               list = list->next;
        }
+       return head;
+}
+
+void free_commit_list(struct commit_list *list)
+{
+       while (list)
+               pop_commit(&list);
 }
 
 struct commit_list * commit_list_insert_by_date(struct commit *item, struct commit_list **list)
@@ -390,26 +555,38 @@ struct commit_list * commit_list_insert_by_date(struct commit *item, struct comm
        return commit_list_insert(item, pp);
 }
 
+static int commit_list_compare_by_date(const void *a, const void *b)
+{
+       timestamp_t a_date = ((const struct commit_list *)a)->item->date;
+       timestamp_t b_date = ((const struct commit_list *)b)->item->date;
+       if (a_date < b_date)
+               return 1;
+       if (a_date > b_date)
+               return -1;
+       return 0;
+}
+
+static void *commit_list_get_next(const void *a)
+{
+       return ((const struct commit_list *)a)->next;
+}
+
+static void commit_list_set_next(void *a, void *next)
+{
+       ((struct commit_list *)a)->next = next;
+}
 
 void commit_list_sort_by_date(struct commit_list **list)
 {
-       struct commit_list *ret = NULL;
-       while (*list) {
-               commit_list_insert_by_date((*list)->item, &ret);
-               *list = (*list)->next;
-       }
-       *list = ret;
+       *list = llist_mergesort(*list, commit_list_get_next, commit_list_set_next,
+                               commit_list_compare_by_date);
 }
 
 struct commit *pop_most_recent_commit(struct commit_list **list,
                                      unsigned int mark)
 {
-       struct commit *ret = (*list)->item;
+       struct commit *ret = pop_commit(list);
        struct commit_list *parents = ret->parents;
-       struct commit_list *old = *list;
-
-       *list = (*list)->next;
-       free(old);
 
        while (parents) {
                struct commit *commit = parents->item;
@@ -444,26 +621,21 @@ static void clear_commit_marks_1(struct commit_list **plist,
        }
 }
 
-void clear_commit_marks(struct commit *commit, unsigned int mark)
+void clear_commit_marks_many(int nr, struct commit **commit, unsigned int mark)
 {
        struct commit_list *list = NULL;
-       commit_list_insert(commit, &list);
+
+       while (nr--) {
+               clear_commit_marks_1(&list, *commit, mark);
+               commit++;
+       }
        while (list)
                clear_commit_marks_1(&list, pop_commit(&list), mark);
 }
 
-void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark)
+void clear_commit_marks(struct commit *commit, unsigned int mark)
 {
-       struct object *object;
-       struct commit *commit;
-       unsigned int i;
-
-       for (i = 0; i < a->nr; i++) {
-               object = a->objects[i].item;
-               commit = lookup_commit_reference_gently(object->sha1, 1);
-               if (commit)
-                       clear_commit_marks(commit, mark);
-       }
+       clear_commit_marks_many(1, &commit, mark);
 }
 
 struct commit *pop_commit(struct commit_list **stack)
@@ -479,32 +651,136 @@ struct commit *pop_commit(struct commit_list **stack)
 }
 
 /*
+ * Topological sort support
+ */
+
+/* count number of children that have not been emitted */
+define_commit_slab(indegree_slab, int);
+
+define_commit_slab(author_date_slab, timestamp_t);
+
+void record_author_date(struct author_date_slab *author_date,
+                       struct commit *commit)
+{
+       const char *buffer = get_commit_buffer(commit, NULL);
+       struct ident_split ident;
+       const char *ident_line;
+       size_t ident_len;
+       char *date_end;
+       timestamp_t date;
+
+       ident_line = find_commit_header(buffer, "author", &ident_len);
+       if (!ident_line)
+               goto fail_exit; /* no author line */
+       if (split_ident_line(&ident, ident_line, ident_len) ||
+           !ident.date_begin || !ident.date_end)
+               goto fail_exit; /* malformed "author" line */
+
+       date = parse_timestamp(ident.date_begin, &date_end, 10);
+       if (date_end != ident.date_end)
+               goto fail_exit; /* malformed date */
+       *(author_date_slab_at(author_date, commit)) = date;
+
+fail_exit:
+       unuse_commit_buffer(commit, buffer);
+}
+
+int compare_commits_by_author_date(const void *a_, const void *b_,
+                                  void *cb_data)
+{
+       const struct commit *a = a_, *b = b_;
+       struct author_date_slab *author_date = cb_data;
+       timestamp_t a_date = *(author_date_slab_at(author_date, a));
+       timestamp_t b_date = *(author_date_slab_at(author_date, b));
+
+       /* newer commits with larger date first */
+       if (a_date < b_date)
+               return 1;
+       else if (a_date > b_date)
+               return -1;
+       return 0;
+}
+
+int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_, void *unused)
+{
+       const struct commit *a = a_, *b = b_;
+
+       /* newer commits first */
+       if (a->generation < b->generation)
+               return 1;
+       else if (a->generation > b->generation)
+               return -1;
+
+       /* use date as a heuristic when generations are equal */
+       if (a->date < b->date)
+               return 1;
+       else if (a->date > b->date)
+               return -1;
+       return 0;
+}
+
+int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
+{
+       const struct commit *a = a_, *b = b_;
+       /* newer commits with larger date first */
+       if (a->date < b->date)
+               return 1;
+       else if (a->date > b->date)
+               return -1;
+       return 0;
+}
+
+/*
  * Performs an in-place topological sort on the list supplied.
  */
-void sort_in_topological_order(struct commit_list ** list, int lifo)
+void sort_in_topological_order(struct commit_list **list, enum rev_sort_order sort_order)
 {
        struct commit_list *next, *orig = *list;
-       struct commit_list *work, **insert;
        struct commit_list **pptr;
+       struct indegree_slab indegree;
+       struct prio_queue queue;
+       struct commit *commit;
+       struct author_date_slab author_date;
 
        if (!orig)
                return;
        *list = NULL;
 
+       init_indegree_slab(&indegree);
+       memset(&queue, '\0', sizeof(queue));
+
+       switch (sort_order) {
+       default: /* REV_SORT_IN_GRAPH_ORDER */
+               queue.compare = NULL;
+               break;
+       case REV_SORT_BY_COMMIT_DATE:
+               queue.compare = compare_commits_by_commit_date;
+               break;
+       case REV_SORT_BY_AUTHOR_DATE:
+               init_author_date_slab(&author_date);
+               queue.compare = compare_commits_by_author_date;
+               queue.cb_data = &author_date;
+               break;
+       }
+
        /* Mark them and clear the indegree */
        for (next = orig; next; next = next->next) {
                struct commit *commit = next->item;
-               commit->indegree = 1;
+               *(indegree_slab_at(&indegree, commit)) = 1;
+               /* also record the author dates, if needed */
+               if (sort_order == REV_SORT_BY_AUTHOR_DATE)
+                       record_author_date(&author_date, commit);
        }
 
        /* update the indegree */
        for (next = orig; next; next = next->next) {
-               struct commit_list * parents = next->item->parents;
+               struct commit_list *parents = next->item->parents;
                while (parents) {
                        struct commit *parent = parents->item;
+                       int *pi = indegree_slab_at(&indegree, parent);
 
-                       if (parent->indegree)
-                               parent->indegree++;
+                       if (*pi)
+                               (*pi)++;
                        parents = parents->next;
                }
        }
@@ -516,34 +792,33 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
         *
         * the tips serve as a starting set for the work queue.
         */
-       work = NULL;
-       insert = &work;
        for (next = orig; next; next = next->next) {
                struct commit *commit = next->item;
 
-               if (commit->indegree == 1)
-                       insert = &commit_list_insert(commit, insert)->next;
+               if (*(indegree_slab_at(&indegree, commit)) == 1)
+                       prio_queue_put(&queue, commit);
        }
 
-       /* process the list in topological order */
-       if (!lifo)
-               commit_list_sort_by_date(&work);
+       /*
+        * This is unfortunate; the initial tips need to be shown
+        * in the order given from the revision traversal machinery.
+        */
+       if (sort_order == REV_SORT_IN_GRAPH_ORDER)
+               prio_queue_reverse(&queue);
+
+       /* We no longer need the commit list */
+       free_commit_list(orig);
 
        pptr = list;
        *list = NULL;
-       while (work) {
-               struct commit *commit;
-               struct commit_list *parents, *work_item;
-
-               work_item = work;
-               work = work_item->next;
-               work_item->next = NULL;
+       while ((commit = prio_queue_get(&queue)) != NULL) {
+               struct commit_list *parents;
 
-               commit = work_item->item;
                for (parents = commit->parents; parents ; parents = parents->next) {
                        struct commit *parent = parents->item;
+                       int *pi = indegree_slab_at(&indegree, parent);
 
-                       if (!parent->indegree)
+                       if (!*pi)
                                continue;
 
                        /*
@@ -551,303 +826,102 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
                         * when all their children have been emitted thereby
                         * guaranteeing topological order.
                         */
-                       if (--parent->indegree == 1) {
-                               if (!lifo)
-                                       commit_list_insert_by_date(parent, &work);
-                               else
-                                       commit_list_insert(parent, &work);
-                       }
+                       if (--(*pi) == 1)
+                               prio_queue_put(&queue, parent);
                }
                /*
-                * work_item is a commit all of whose children
-                * have already been emitted. we can emit it now.
+                * all children of commit have already been
+                * emitted. we can emit it now.
                 */
-               commit->indegree = 0;
-               *pptr = work_item;
-               pptr = &work_item->next;
-       }
-}
-
-/* merge-base stuff */
-
-/* bits #0..15 in revision.h */
-#define PARENT1                (1u<<16)
-#define PARENT2                (1u<<17)
-#define STALE          (1u<<18)
-#define RESULT         (1u<<19)
+               *(indegree_slab_at(&indegree, commit)) = 0;
 
-static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
-
-static struct commit *interesting(struct commit_list *list)
-{
-       while (list) {
-               struct commit *commit = list->item;
-               list = list->next;
-               if (commit->object.flags & STALE)
-                       continue;
-               return commit;
+               pptr = &commit_list_insert(commit, pptr)->next;
        }
-       return NULL;
-}
 
-static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
-{
-       struct commit_list *list = NULL;
-       struct commit_list *result = NULL;
-       int i;
-
-       for (i = 0; i < n; i++) {
-               if (one == twos[i])
-                       /*
-                        * We do not mark this even with RESULT so we do not
-                        * have to clean it up.
-                        */
-                       return commit_list_insert(one, &result);
-       }
-
-       if (parse_commit(one))
-               return NULL;
-       for (i = 0; i < n; i++) {
-               if (parse_commit(twos[i]))
-                       return NULL;
-       }
-
-       one->object.flags |= PARENT1;
-       commit_list_insert_by_date(one, &list);
-       for (i = 0; i < n; i++) {
-               twos[i]->object.flags |= PARENT2;
-               commit_list_insert_by_date(twos[i], &list);
-       }
-
-       while (interesting(list)) {
-               struct commit *commit;
-               struct commit_list *parents;
-               struct commit_list *next;
-               int flags;
-
-               commit = list->item;
-               next = list->next;
-               free(list);
-               list = next;
-
-               flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
-               if (flags == (PARENT1 | PARENT2)) {
-                       if (!(commit->object.flags & RESULT)) {
-                               commit->object.flags |= RESULT;
-                               commit_list_insert_by_date(commit, &result);
-                       }
-                       /* Mark parents of a found merge stale */
-                       flags |= STALE;
-               }
-               parents = commit->parents;
-               while (parents) {
-                       struct commit *p = parents->item;
-                       parents = parents->next;
-                       if ((p->object.flags & flags) == flags)
-                               continue;
-                       if (parse_commit(p))
-                               return NULL;
-                       p->object.flags |= flags;
-                       commit_list_insert_by_date(p, &list);
-               }
-       }
-
-       /* Clean up the result to remove stale ones */
-       free_commit_list(list);
-       list = result; result = NULL;
-       while (list) {
-               struct commit_list *next = list->next;
-               if (!(list->item->object.flags & STALE))
-                       commit_list_insert_by_date(list->item, &result);
-               free(list);
-               list = next;
-       }
-       return result;
+       clear_indegree_slab(&indegree);
+       clear_prio_queue(&queue);
+       if (sort_order == REV_SORT_BY_AUTHOR_DATE)
+               clear_author_date_slab(&author_date);
 }
 
-struct commit_list *get_octopus_merge_bases(struct commit_list *in)
-{
-       struct commit_list *i, *j, *k, *ret = NULL;
-       struct commit_list **pptr = &ret;
+struct rev_collect {
+       struct commit **commit;
+       int nr;
+       int alloc;
+       unsigned int initial : 1;
+};
 
-       for (i = in; i; i = i->next) {
-               if (!ret)
-                       pptr = &commit_list_insert(i->item, pptr)->next;
-               else {
-                       struct commit_list *new = NULL, *end = NULL;
-
-                       for (j = ret; j; j = j->next) {
-                               struct commit_list *bases;
-                               bases = get_merge_bases(i->item, j->item, 1);
-                               if (!new)
-                                       new = bases;
-                               else
-                                       end->next = bases;
-                               for (k = bases; k; k = k->next)
-                                       end = k;
-                       }
-                       ret = new;
-               }
-       }
-       return ret;
-}
-
-struct commit_list *get_merge_bases_many(struct commit *one,
-                                        int n,
-                                        struct commit **twos,
-                                        int cleanup)
+static void add_one_commit(struct object_id *oid, struct rev_collect *revs)
 {
-       struct commit_list *list;
-       struct commit **rslt;
-       struct commit_list *result;
-       int cnt, i, j;
-
-       result = merge_bases_many(one, n, twos);
-       for (i = 0; i < n; i++) {
-               if (one == twos[i])
-                       return result;
-       }
-       if (!result || !result->next) {
-               if (cleanup) {
-                       clear_commit_marks(one, all_flags);
-                       for (i = 0; i < n; i++)
-                               clear_commit_marks(twos[i], all_flags);
-               }
-               return result;
-       }
+       struct commit *commit;
 
-       /* There are more than one */
-       cnt = 0;
-       list = result;
-       while (list) {
-               list = list->next;
-               cnt++;
-       }
-       rslt = xcalloc(cnt, sizeof(*rslt));
-       for (list = result, i = 0; list; list = list->next)
-               rslt[i++] = list->item;
-       free_commit_list(result);
-
-       clear_commit_marks(one, all_flags);
-       for (i = 0; i < n; i++)
-               clear_commit_marks(twos[i], all_flags);
-       for (i = 0; i < cnt - 1; i++) {
-               for (j = i+1; j < cnt; j++) {
-                       if (!rslt[i] || !rslt[j])
-                               continue;
-                       result = merge_bases_many(rslt[i], 1, &rslt[j]);
-                       clear_commit_marks(rslt[i], all_flags);
-                       clear_commit_marks(rslt[j], all_flags);
-                       for (list = result; list; list = list->next) {
-                               if (rslt[i] == list->item)
-                                       rslt[i] = NULL;
-                               if (rslt[j] == list->item)
-                                       rslt[j] = NULL;
-                       }
-               }
-       }
+       if (is_null_oid(oid))
+               return;
 
-       /* Surviving ones in rslt[] are the independent results */
-       result = NULL;
-       for (i = 0; i < cnt; i++) {
-               if (rslt[i])
-                       commit_list_insert_by_date(rslt[i], &result);
-       }
-       free(rslt);
-       return result;
-}
+       commit = lookup_commit(the_repository, oid);
+       if (!commit ||
+           (commit->object.flags & TMP_MARK) ||
+           parse_commit(commit))
+               return;
 
-struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
-                                   int cleanup)
-{
-       return get_merge_bases_many(one, 1, &two, cleanup);
+       ALLOC_GROW(revs->commit, revs->nr + 1, revs->alloc);
+       revs->commit[revs->nr++] = commit;
+       commit->object.flags |= TMP_MARK;
 }
 
-int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
+static int collect_one_reflog_ent(struct object_id *ooid, struct object_id *noid,
+                                 const char *ident, timestamp_t timestamp,
+                                 int tz, const char *message, void *cbdata)
 {
-       if (!with_commit)
-               return 1;
-       while (with_commit) {
-               struct commit *other;
+       struct rev_collect *revs = cbdata;
 
-               other = with_commit->item;
-               with_commit = with_commit->next;
-               if (in_merge_bases(other, &commit, 1))
-                       return 1;
+       if (revs->initial) {
+               revs->initial = 0;
+               add_one_commit(ooid, revs);
        }
+       add_one_commit(noid, revs);
        return 0;
 }
 
-int in_merge_bases(struct commit *commit, struct commit **reference, int num)
+struct commit *get_fork_point(const char *refname, struct commit *commit)
 {
-       struct commit_list *bases, *b;
-       int ret = 0;
+       struct object_id oid;
+       struct rev_collect revs;
+       struct commit_list *bases;
+       int i;
+       struct commit *ret = NULL;
 
-       if (num == 1)
-               bases = get_merge_bases(commit, *reference, 1);
-       else
-               die("not yet");
-       for (b = bases; b; b = b->next) {
-               if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
-                       ret = 1;
-                       break;
-               }
-       }
+       memset(&revs, 0, sizeof(revs));
+       revs.initial = 1;
+       for_each_reflog_ent(refname, collect_one_reflog_ent, &revs);
 
-       free_commit_list(bases);
-       return ret;
-}
+       if (!revs.nr && !get_oid(refname, &oid))
+               add_one_commit(&oid, &revs);
 
-struct commit_list *reduce_heads(struct commit_list *heads)
-{
-       struct commit_list *p;
-       struct commit_list *result = NULL, **tail = &result;
-       struct commit **other;
-       size_t num_head, num_other;
+       for (i = 0; i < revs.nr; i++)
+               revs.commit[i]->object.flags &= ~TMP_MARK;
 
-       if (!heads)
-               return NULL;
+       bases = get_merge_bases_many(commit, revs.nr, revs.commit);
 
-       /* Avoid unnecessary reallocations */
-       for (p = heads, num_head = 0; p; p = p->next)
-               num_head++;
-       other = xcalloc(sizeof(*other), num_head);
+       /*
+        * There should be one and only one merge base, when we found
+        * a common ancestor among reflog entries.
+        */
+       if (!bases || bases->next)
+               goto cleanup_return;
 
-       /* For each commit, see if it can be reached by others */
-       for (p = heads; p; p = p->next) {
-               struct commit_list *q, *base;
+       /* And the found one must be one of the reflog entries */
+       for (i = 0; i < revs.nr; i++)
+               if (&bases->item->object == &revs.commit[i]->object)
+                       break; /* found */
+       if (revs.nr <= i)
+               goto cleanup_return;
 
-               /* Do we already have this in the result? */
-               for (q = result; q; q = q->next)
-                       if (p->item == q->item)
-                               break;
-               if (q)
-                       continue;
+       ret = bases->item;
 
-               num_other = 0;
-               for (q = heads; q; q = q->next) {
-                       if (p->item == q->item)
-                               continue;
-                       other[num_other++] = q->item;
-               }
-               if (num_other)
-                       base = get_merge_bases_many(p->item, num_other, other, 1);
-               else
-                       base = NULL;
-               /*
-                * If p->item does not have anything common with other
-                * commits, there won't be any merge base.  If it is
-                * reachable from some of the others, p->item will be
-                * the merge base.  If its history is connected with
-                * others, but p->item is not reachable by others, we
-                * will get something other than p->item back.
-                */
-               if (!base || (base->item != p->item))
-                       tail = &(commit_list_insert(p->item, tail)->next);
-               free_commit_list(base);
-       }
-       free(other);
-       return result;
+cleanup_return:
+       free_commit_list(bases);
+       return ret;
 }
 
 static const char gpg_sig_header[] = "gpgsig";
@@ -857,9 +931,14 @@ static int do_sign_commit(struct strbuf *buf, const char *keyid)
 {
        struct strbuf sig = STRBUF_INIT;
        int inspos, copypos;
+       const char *eoh;
 
        /* find the end of the header */
-       inspos = strstr(buf->buf, "\n\n") - buf->buf + 1;
+       eoh = strstr(buf->buf, "\n\n");
+       if (!eoh)
+               inspos = buf->len;
+       else
+               inspos = eoh - buf->buf + 1;
 
        if (!keyid || !*keyid)
                keyid = get_signing_key();
@@ -886,17 +965,14 @@ static int do_sign_commit(struct strbuf *buf, const char *keyid)
        return 0;
 }
 
-int parse_signed_commit(const unsigned char *sha1,
+int parse_signed_commit(const struct commit *commit,
                        struct strbuf *payload, struct strbuf *signature)
 {
+
        unsigned long size;
-       enum object_type type;
-       char *buffer = read_sha1_file(sha1, &type, &size);
+       const char *buffer = get_commit_buffer(commit, &size);
        int in_signature, saw_signature = -1;
-       char *line, *tail;
-
-       if (!buffer || type != OBJ_COMMIT)
-               goto cleanup;
+       const char *line, *tail;
 
        line = buffer;
        tail = buffer + size;
@@ -904,12 +980,12 @@ int parse_signed_commit(const unsigned char *sha1,
        saw_signature = 0;
        while (line < tail) {
                const char *sig = NULL;
-               char *next = memchr(line, '\n', tail - line);
+               const char *next = memchr(line, '\n', tail - line);
 
                next = next ? next + 1 : tail;
                if (in_signature && line[0] == ' ')
                        sig = line + 1;
-               else if (!prefixcmp(line, gpg_sig_header) &&
+               else if (starts_with(line, gpg_sig_header) &&
                         line[gpg_sig_header_len] == ' ')
                        sig = line + gpg_sig_header_len + 1;
                if (sig) {
@@ -925,11 +1001,44 @@ int parse_signed_commit(const unsigned char *sha1,
                }
                line = next;
        }
- cleanup:
-       free(buffer);
+       unuse_commit_buffer(commit, buffer);
        return saw_signature;
 }
 
+int remove_signature(struct strbuf *buf)
+{
+       const char *line = buf->buf;
+       const char *tail = buf->buf + buf->len;
+       int in_signature = 0;
+       const char *sig_start = NULL;
+       const char *sig_end = NULL;
+
+       while (line < tail) {
+               const char *next = memchr(line, '\n', tail - line);
+               next = next ? next + 1 : tail;
+
+               if (in_signature && line[0] == ' ')
+                       sig_end = next;
+               else if (starts_with(line, gpg_sig_header) &&
+                        line[gpg_sig_header_len] == ' ') {
+                       sig_start = line;
+                       sig_end = next;
+                       in_signature = 1;
+               } else {
+                       if (*line == '\n')
+                               /* dump the whole remainder of the buffer */
+                               next = tail;
+                       in_signature = 0;
+               }
+               line = next;
+       }
+
+       if (sig_start)
+               strbuf_remove(buf, sig_start - buf->buf, sig_end - sig_start);
+
+       return sig_start != NULL;
+}
+
 static void handle_signed_tag(struct commit *parent, struct commit_extra_header ***tail)
 {
        struct merge_remote_desc *desc;
@@ -941,7 +1050,7 @@ static void handle_signed_tag(struct commit *parent, struct commit_extra_header
        desc = merge_remote_util(parent);
        if (!desc || !desc->obj)
                return;
-       buf = read_sha1_file(desc->obj->sha1, &type, &size);
+       buf = read_object_file(&desc->obj->oid, &type, &size);
        if (!buf || type != OBJ_TAG)
                goto free_return;
        len = parse_signature(buf, size);
@@ -970,6 +1079,54 @@ free_return:
        free(buf);
 }
 
+int check_commit_signature(const struct commit *commit, struct signature_check *sigc)
+{
+       struct strbuf payload = STRBUF_INIT;
+       struct strbuf signature = STRBUF_INIT;
+       int ret = 1;
+
+       sigc->result = 'N';
+
+       if (parse_signed_commit(commit, &payload, &signature) <= 0)
+               goto out;
+       ret = check_signature(payload.buf, payload.len, signature.buf,
+               signature.len, sigc);
+
+ out:
+       strbuf_release(&payload);
+       strbuf_release(&signature);
+
+       return ret;
+}
+
+void verify_merge_signature(struct commit *commit, int verbosity)
+{
+       char hex[GIT_MAX_HEXSZ + 1];
+       struct signature_check signature_check;
+       memset(&signature_check, 0, sizeof(signature_check));
+
+       check_commit_signature(commit, &signature_check);
+
+       find_unique_abbrev_r(hex, &commit->object.oid, DEFAULT_ABBREV);
+       switch (signature_check.result) {
+       case 'G':
+               break;
+       case 'U':
+               die(_("Commit %s has an untrusted GPG signature, "
+                     "allegedly by %s."), hex, signature_check.signer);
+       case 'B':
+               die(_("Commit %s has a bad GPG signature "
+                     "allegedly by %s."), hex, signature_check.signer);
+       default: /* 'N' */
+               die(_("Commit %s does not have a GPG signature."), hex);
+       }
+       if (verbosity >= 0 && signature_check.result == 'G')
+               printf(_("Commit %s has a good GPG signature by %s\n"),
+                      hex, signature_check.signer);
+
+       signature_check_clear(&signature_check);
+}
+
 void append_merge_tag_headers(struct commit_list *parents,
                              struct commit_extra_header ***tail)
 {
@@ -995,21 +1152,34 @@ struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
 {
        struct commit_extra_header *extra = NULL;
        unsigned long size;
-       enum object_type type;
-       char *buffer = read_sha1_file(commit->object.sha1, &type, &size);
-       if (buffer && type == OBJ_COMMIT)
-               extra = read_commit_extra_header_lines(buffer, size, exclude);
-       free(buffer);
+       const char *buffer = get_commit_buffer(commit, &size);
+       extra = read_commit_extra_header_lines(buffer, size, exclude);
+       unuse_commit_buffer(commit, buffer);
        return extra;
 }
 
+int for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data)
+{
+       struct commit_extra_header *extra, *to_free;
+       int res = 0;
+
+       to_free = read_commit_extra_headers(commit, NULL);
+       for (extra = to_free; !res && extra; extra = extra->next) {
+               if (strcmp(extra->key, "mergetag"))
+                       continue; /* not a merge tag */
+               res = fn(commit, extra, data);
+       }
+       free_commit_extra_headers(to_free);
+       return res;
+}
+
 static inline int standard_header_field(const char *field, size_t len)
 {
-       return ((len == 4 && !memcmp(field, "tree ", 5)) ||
-               (len == 6 && !memcmp(field, "parent ", 7)) ||
-               (len == 6 && !memcmp(field, "author ", 7)) ||
-               (len == 9 && !memcmp(field, "committer ", 10)) ||
-               (len == 8 && !memcmp(field, "encoding ", 9)));
+       return ((len == 4 && !memcmp(field, "tree", 4)) ||
+               (len == 6 && !memcmp(field, "parent", 6)) ||
+               (len == 6 && !memcmp(field, "author", 6)) ||
+               (len == 9 && !memcmp(field, "committer", 9)) ||
+               (len == 8 && !memcmp(field, "encoding", 8)));
 }
 
 static int excluded_header_field(const char *field, size_t len, const char **exclude)
@@ -1019,16 +1189,16 @@ static int excluded_header_field(const char *field, size_t len, const char **exc
 
        while (*exclude) {
                size_t xlen = strlen(*exclude);
-               if (len == xlen &&
-                   !memcmp(field, *exclude, xlen) && field[xlen] == ' ')
+               if (len == xlen && !memcmp(field, *exclude, xlen))
                        return 1;
                exclude++;
        }
        return 0;
 }
 
-struct commit_extra_header *read_commit_extra_header_lines(const char *buffer, size_t size,
-                                                          const char **exclude)
+static struct commit_extra_header *read_commit_extra_header_lines(
+       const char *buffer, size_t size,
+       const char **exclude)
 {
        struct commit_extra_header *extra = NULL, **tail = &extra, *it = NULL;
        const char *line, *next, *eof, *eob;
@@ -1050,12 +1220,11 @@ struct commit_extra_header *read_commit_extra_header_lines(const char *buffer, s
                strbuf_reset(&buf);
                it = NULL;
 
-               eof = strchr(line, ' ');
-               if (next <= eof)
+               eof = memchr(line, ' ', next - line);
+               if (!eof)
                        eof = next;
-
-               if (standard_header_field(line, eof - line) ||
-                   excluded_header_field(line, eof - line, exclude))
+               else if (standard_header_field(line, eof - line) ||
+                        excluded_header_field(line, eof - line, exclude))
                        continue;
 
                it = xcalloc(1, sizeof(*it));
@@ -1081,27 +1250,138 @@ void free_commit_extra_headers(struct commit_extra_header *extra)
        }
 }
 
-int commit_tree(const struct strbuf *msg, unsigned char *tree,
-               struct commit_list *parents, unsigned char *ret,
+int commit_tree(const char *msg, size_t msg_len, const struct object_id *tree,
+               struct commit_list *parents, struct object_id *ret,
                const char *author, const char *sign_commit)
 {
        struct commit_extra_header *extra = NULL, **tail = &extra;
        int result;
 
        append_merge_tag_headers(parents, &tail);
-       result = commit_tree_extended(msg, tree, parents, ret,
+       result = commit_tree_extended(msg, msg_len, tree, parents, ret,
                                      author, sign_commit, extra);
        free_commit_extra_headers(extra);
        return result;
 }
 
+static int find_invalid_utf8(const char *buf, int len)
+{
+       int offset = 0;
+       static const unsigned int max_codepoint[] = {
+               0x7f, 0x7ff, 0xffff, 0x10ffff
+       };
+
+       while (len) {
+               unsigned char c = *buf++;
+               int bytes, bad_offset;
+               unsigned int codepoint;
+               unsigned int min_val, max_val;
+
+               len--;
+               offset++;
+
+               /* Simple US-ASCII? No worries. */
+               if (c < 0x80)
+                       continue;
+
+               bad_offset = offset-1;
+
+               /*
+                * Count how many more high bits set: that's how
+                * many more bytes this sequence should have.
+                */
+               bytes = 0;
+               while (c & 0x40) {
+                       c <<= 1;
+                       bytes++;
+               }
+
+               /*
+                * Must be between 1 and 3 more bytes.  Longer sequences result in
+                * codepoints beyond U+10FFFF, which are guaranteed never to exist.
+                */
+               if (bytes < 1 || 3 < bytes)
+                       return bad_offset;
+
+               /* Do we *have* that many bytes? */
+               if (len < bytes)
+                       return bad_offset;
+
+               /*
+                * Place the encoded bits at the bottom of the value and compute the
+                * valid range.
+                */
+               codepoint = (c & 0x7f) >> bytes;
+               min_val = max_codepoint[bytes-1] + 1;
+               max_val = max_codepoint[bytes];
+
+               offset += bytes;
+               len -= bytes;
+
+               /* And verify that they are good continuation bytes */
+               do {
+                       codepoint <<= 6;
+                       codepoint |= *buf & 0x3f;
+                       if ((*buf++ & 0xc0) != 0x80)
+                               return bad_offset;
+               } while (--bytes);
+
+               /* Reject codepoints that are out of range for the sequence length. */
+               if (codepoint < min_val || codepoint > max_val)
+                       return bad_offset;
+               /* Surrogates are only for UTF-16 and cannot be encoded in UTF-8. */
+               if ((codepoint & 0x1ff800) == 0xd800)
+                       return bad_offset;
+               /* U+xxFFFE and U+xxFFFF are guaranteed non-characters. */
+               if ((codepoint & 0xfffe) == 0xfffe)
+                       return bad_offset;
+               /* So are anything in the range U+FDD0..U+FDEF. */
+               if (codepoint >= 0xfdd0 && codepoint <= 0xfdef)
+                       return bad_offset;
+       }
+       return -1;
+}
+
+/*
+ * This verifies that the buffer is in proper utf8 format.
+ *
+ * If it isn't, it assumes any non-utf8 characters are Latin1,
+ * and does the conversion.
+ */
+static int verify_utf8(struct strbuf *buf)
+{
+       int ok = 1;
+       long pos = 0;
+
+       for (;;) {
+               int bad;
+               unsigned char c;
+               unsigned char replace[2];
+
+               bad = find_invalid_utf8(buf->buf + pos, buf->len - pos);
+               if (bad < 0)
+                       return ok;
+               pos += bad;
+               ok = 0;
+               c = buf->buf[pos];
+               strbuf_remove(buf, pos, 1);
+
+               /* We know 'c' must be in the range 128-255 */
+               replace[0] = 0xc0 + (c >> 6);
+               replace[1] = 0x80 + (c & 0x3f);
+               strbuf_insert(buf, pos, replace, 2);
+               pos += 2;
+       }
+}
+
 static const char commit_utf8_warn[] =
-"Warning: commit message does not conform to UTF-8.\n"
-"You may want to amend it after fixing the message, or set the config\n"
-"variable i18n.commitencoding to the encoding your project uses.\n";
+N_("Warning: commit message did not conform to UTF-8.\n"
+   "You may want to amend it after fixing the message, or set the config\n"
+   "variable i18n.commitencoding to the encoding your project uses.\n");
 
-int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
-                        struct commit_list *parents, unsigned char *ret,
+int commit_tree_extended(const char *msg, size_t msg_len,
+                        const struct object_id *tree,
+                        struct commit_list *parents, struct object_id *ret,
                         const char *author, const char *sign_commit,
                         struct commit_extra_header *extra)
 {
@@ -1109,16 +1389,16 @@ int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
        int encoding_is_utf8;
        struct strbuf buffer;
 
-       assert_sha1_type(tree, OBJ_TREE);
+       assert_oid_type(tree, OBJ_TREE);
 
-       if (memchr(msg->buf, '\0', msg->len))
+       if (memchr(msg, '\0', msg_len))
                return error("a NUL byte in commit log message not allowed.");
 
        /* Not having i18n.commitencoding is the same as having utf-8 */
        encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 
        strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
-       strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
+       strbuf_addf(&buffer, "tree %s\n", oid_to_hex(tree));
 
        /*
         * NOTE! This ordering means that the same exact tree merged with a
@@ -1126,20 +1406,16 @@ int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
         * if everything else stays the same.
         */
        while (parents) {
-               struct commit_list *next = parents->next;
-               struct commit *parent = parents->item;
-
+               struct commit *parent = pop_commit(&parents);
                strbuf_addf(&buffer, "parent %s\n",
-                           sha1_to_hex(parent->object.sha1));
-               free(parents);
-               parents = next;
+                           oid_to_hex(&parent->object.oid));
        }
 
        /* Person/date information */
        if (!author)
-               author = git_author_info(IDENT_ERROR_ON_NO_NAME);
+               author = git_author_info(IDENT_STRICT);
        strbuf_addf(&buffer, "author %s\n", author);
-       strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
+       strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
        if (!encoding_is_utf8)
                strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 
@@ -1150,35 +1426,145 @@ int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
        strbuf_addch(&buffer, '\n');
 
        /* And add the comment */
-       strbuf_addbuf(&buffer, msg);
+       strbuf_add(&buffer, msg, msg_len);
 
        /* And check the encoding */
-       if (encoding_is_utf8 && !is_utf8(buffer.buf))
-               fprintf(stderr, commit_utf8_warn);
+       if (encoding_is_utf8 && !verify_utf8(&buffer))
+               fprintf(stderr, _(commit_utf8_warn));
 
-       if (sign_commit && do_sign_commit(&buffer, sign_commit))
-               return -1;
+       if (sign_commit && do_sign_commit(&buffer, sign_commit)) {
+               result = -1;
+               goto out;
+       }
 
-       result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
+       result = write_object_file(buffer.buf, buffer.len, commit_type, ret);
+out:
        strbuf_release(&buffer);
        return result;
 }
 
+define_commit_slab(merge_desc_slab, struct merge_remote_desc *);
+static struct merge_desc_slab merge_desc_slab = COMMIT_SLAB_INIT(1, merge_desc_slab);
+
+struct merge_remote_desc *merge_remote_util(struct commit *commit)
+{
+       return *merge_desc_slab_at(&merge_desc_slab, commit);
+}
+
+void set_merge_remote_desc(struct commit *commit,
+                          const char *name, struct object *obj)
+{
+       struct merge_remote_desc *desc;
+       FLEX_ALLOC_STR(desc, name, name);
+       desc->obj = obj;
+       *merge_desc_slab_at(&merge_desc_slab, commit) = desc;
+}
+
 struct commit *get_merge_parent(const char *name)
 {
        struct object *obj;
        struct commit *commit;
-       unsigned char sha1[20];
-       if (get_sha1(name, sha1))
+       struct object_id oid;
+       if (get_oid(name, &oid))
                return NULL;
-       obj = parse_object(sha1);
+       obj = parse_object(the_repository, &oid);
        commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
-       if (commit && !commit->util) {
-               struct merge_remote_desc *desc;
-               desc = xmalloc(sizeof(*desc));
-               desc->obj = obj;
-               desc->name = strdup(name);
-               commit->util = desc;
-       }
+       if (commit && !merge_remote_util(commit))
+               set_merge_remote_desc(commit, name, obj);
        return commit;
 }
+
+/*
+ * Append a commit to the end of the commit_list.
+ *
+ * next starts by pointing to the variable that holds the head of an
+ * empty commit_list, and is updated to point to the "next" field of
+ * the last item on the list as new commits are appended.
+ *
+ * Usage example:
+ *
+ *     struct commit_list *list;
+ *     struct commit_list **next = &list;
+ *
+ *     next = commit_list_append(c1, next);
+ *     next = commit_list_append(c2, next);
+ *     assert(commit_list_count(list) == 2);
+ *     return list;
+ */
+struct commit_list **commit_list_append(struct commit *commit,
+                                       struct commit_list **next)
+{
+       struct commit_list *new_commit = xmalloc(sizeof(struct commit_list));
+       new_commit->item = commit;
+       *next = new_commit;
+       new_commit->next = NULL;
+       return &new_commit->next;
+}
+
+const char *find_commit_header(const char *msg, const char *key, size_t *out_len)
+{
+       int key_len = strlen(key);
+       const char *line = msg;
+
+       while (line) {
+               const char *eol = strchrnul(line, '\n');
+
+               if (line == eol)
+                       return NULL;
+
+               if (eol - line > key_len &&
+                   !strncmp(line, key, key_len) &&
+                   line[key_len] == ' ') {
+                       *out_len = eol - line - key_len - 1;
+                       return line + key_len + 1;
+               }
+               line = *eol ? eol + 1 : NULL;
+       }
+       return NULL;
+}
+
+/*
+ * Inspect the given string and determine the true "end" of the log message, in
+ * order to find where to put a new Signed-off-by: line.  Ignored are
+ * trailing comment lines and blank lines.  To support "git commit -s
+ * --amend" on an existing commit, we also ignore "Conflicts:".  To
+ * support "git commit -v", we truncate at cut lines.
+ *
+ * Returns the number of bytes from the tail to ignore, to be fed as
+ * the second parameter to append_signoff().
+ */
+size_t ignore_non_trailer(const char *buf, size_t len)
+{
+       size_t boc = 0;
+       size_t bol = 0;
+       int in_old_conflicts_block = 0;
+       size_t cutoff = wt_status_locate_end(buf, len);
+
+       while (bol < cutoff) {
+               const char *next_line = memchr(buf + bol, '\n', len - bol);
+
+               if (!next_line)
+                       next_line = buf + len;
+               else
+                       next_line++;
+
+               if (buf[bol] == comment_line_char || buf[bol] == '\n') {
+                       /* is this the first of the run of comments? */
+                       if (!boc)
+                               boc = bol;
+                       /* otherwise, it is just continuing */
+               } else if (starts_with(buf + bol, "Conflicts:\n")) {
+                       in_old_conflicts_block = 1;
+                       if (!boc)
+                               boc = bol;
+               } else if (in_old_conflicts_block && buf[bol] == '\t') {
+                       ; /* a pathname in the conflicts block */
+               } else if (boc) {
+                       /* the previous was not trailing comment */
+                       boc = 0;
+                       in_old_conflicts_block = 0;
+               }
+               bol = next_line - buf;
+       }
+       return boc ? len - boc : len - cutoff;
+}