Merge branch 'jc/sha1-name-more'
authorJunio C Hamano <gitster@pobox.com>
Sun, 22 Jul 2012 19:55:07 +0000 (12:55 -0700)
committerJunio C Hamano <gitster@pobox.com>
Sun, 22 Jul 2012 19:55:07 +0000 (12:55 -0700)
Teaches the object name parser things like a "git describe" output
is always a commit object, "A" in "git log A" must be a committish,
and "A" and "B" in "git log A...B" both must be committish, etc., to
prolong the lifetime of abbreviated object names.

* jc/sha1-name-more: (27 commits)
t1512: match the "other" object names
t1512: ignore whitespaces in wc -l output
rev-parse --disambiguate=<prefix>
rev-parse: A and B in "rev-parse A..B" refer to committish
reset: the command takes committish
commit-tree: the command wants a tree and commits
apply: --build-fake-ancestor expects blobs
sha1_name.c: add support for disambiguating other types
revision.c: the "log" family, except for "show", takes committish
revision.c: allow handle_revision_arg() to take other flags
sha1_name.c: introduce get_sha1_committish()
sha1_name.c: teach lookup context to get_sha1_with_context()
sha1_name.c: many short names can only be committish
sha1_name.c: get_sha1_1() takes lookup flags
sha1_name.c: get_describe_name() by definition groks only commits
sha1_name.c: teach get_short_sha1() a commit-only option
sha1_name.c: allow get_short_sha1() to take other flags
get_sha1(): fix error status regression
sha1_name.c: restructure disambiguation of short names
sha1_name.c: correct misnamed "canonical" and "res"
...

15 files changed:
Documentation/git-rev-parse.txt
builtin/apply.c
builtin/cat-file.c
builtin/commit-tree.c
builtin/log.c
builtin/pack-objects.c
builtin/reset.c
builtin/rev-parse.c
cache.h
commit.c
revision.c
revision.h
setup.c
sha1_name.c
t/t1512-rev-parse-disambiguation.sh [new file with mode: 0755]
index 4cc3e9586fcfd79ddeb7f636141e1a878285b0b5..3c63561f02aca6f934c47a2897f8e50cf4ac5fe5 100644 (file)
@@ -101,6 +101,12 @@ OPTIONS
        The option core.warnAmbiguousRefs is used to select the strict
        abbreviation mode.
 
+--disambiguate=<prefix>::
+       Show every object whose name begins with the given prefix.
+       The <prefix> must be at least 4 hexadecimal digits long to
+       avoid listing each and every object in the repository by
+       mistake.
+
 --all::
        Show all refs found in `refs/`.
 
index ace04c453be447b62b4907c45247f82ef4344033..069cf341b653080e2bae64faa0a00b387f88c961 100644 (file)
@@ -3589,7 +3589,7 @@ static void build_fake_ancestor(struct patch *list, const char *filename)
                name = patch->old_name ? patch->old_name : patch->new_name;
                if (0 < patch->is_new)
                        continue;
-               else if (get_sha1(patch->old_sha1_prefix, sha1))
+               else if (get_sha1_blob(patch->old_sha1_prefix, sha1))
                        /* git diff has no index line for mode/type changes */
                        if (!patch->lines_added && !patch->lines_deleted) {
                                if (get_current_sha1(patch->old_name, sha1))
index 36a9104433e23422aab39b1912e998a7f54cd3f4..af74e775a182bdf764436362cb37471e74930459 100644 (file)
@@ -91,7 +91,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
        unsigned long size;
        struct object_context obj_context;
 
-       if (get_sha1_with_context(obj_name, sha1, &obj_context))
+       if (get_sha1_with_context(obj_name, 0, sha1, &obj_context))
                die("Not a valid object name %s", obj_name);
 
        buf = NULL;
index 164b655df93fea1ec2f63f5238c1ad7a377c8385..cb982c550332abc846eee690f8e33c66db742053 100644 (file)
@@ -48,8 +48,8 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
        if (argc < 2 || !strcmp(argv[1], "-h"))
                usage(commit_tree_usage);
 
-       if (get_sha1(argv[1], tree_sha1))
-               die("Not a valid object name %s", argv[1]);
+       if (get_sha1_tree(argv[1], tree_sha1))
+               die("Not a valid tree object name %s", argv[1]);
 
        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
@@ -57,7 +57,7 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
                        unsigned char sha1[20];
                        if (argc <= ++i)
                                usage(commit_tree_usage);
-                       if (get_sha1(argv[i], sha1))
+                       if (get_sha1_commit(argv[i], sha1))
                                die("Not a valid object name %s", argv[i]);
                        assert_sha1_type(sha1, OBJ_COMMIT);
                        new_parent(lookup_commit(sha1), &parents);
@@ -104,7 +104,7 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
                        continue;
                }
 
-               if (get_sha1(arg, tree_sha1))
+               if (get_sha1_tree(arg, tree_sha1))
                        die("Not a valid object name %s", arg);
                if (got_tree)
                        die("Cannot give more than one trees");
index adcbcf1f2446573c99f00fb2480c8b582237cae1..ecc2793690496531546765516d80032a1cbf8844 100644 (file)
@@ -367,6 +367,7 @@ int cmd_whatchanged(int argc, const char **argv, const char *prefix)
        rev.simplify_history = 0;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
+       opt.revarg_opt = REVARG_COMMITTISH;
        cmd_log_init(argc, argv, prefix, &rev, &opt);
        if (!rev.diffopt.output_format)
                rev.diffopt.output_format = DIFF_FORMAT_RAW;
@@ -557,6 +558,7 @@ int cmd_log(int argc, const char **argv, const char *prefix)
        rev.always_show_header = 1;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
+       opt.revarg_opt = REVARG_COMMITTISH;
        cmd_log_init(argc, argv, prefix, &rev, &opt);
        return cmd_log_walk(&rev);
 }
@@ -1132,6 +1134,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
        rev.subject_prefix = fmt_patch_subject_prefix;
        memset(&s_r_opt, 0, sizeof(s_r_opt));
        s_r_opt.def = "HEAD";
+       s_r_opt.revarg_opt = REVARG_COMMITTISH;
 
        if (default_attach) {
                rev.mime_boundary = default_attach;
index f3348208d89a4fbeb3ae9f79376d7d21a8f9015c..782e7d0c38aa939a7db03266c3e6ff4993e4d2bd 100644 (file)
@@ -2373,7 +2373,7 @@ static void get_object_list(int ac, const char **av)
                        }
                        die("not a rev '%s'", line);
                }
-               if (handle_revision_arg(line, &revs, flags, 1))
+               if (handle_revision_arg(line, &revs, flags, REVARG_CANNOT_BE_FILENAME))
                        die("bad revision '%s'", line);
        }
 
index 4cc34c908446fe2d3db5acf315e47f2768ba07bd..74442bd7663387ab9864927f9c0d511e04e6e379 100644 (file)
@@ -276,7 +276,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
                 * Otherwise, argv[i] could be either <rev> or <paths> and
                 * has to be unambiguous.
                 */
-               else if (!get_sha1(argv[i], sha1)) {
+               else if (!get_sha1_committish(argv[i], sha1)) {
                        /*
                         * Ok, argv[i] looks like a rev; it should not
                         * be a filename.
@@ -289,9 +289,15 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
                }
        }
 
-       if (get_sha1(rev, sha1))
+       if (get_sha1_committish(rev, sha1))
                die(_("Failed to resolve '%s' as a valid ref."), rev);
 
+       /*
+        * NOTE: As "git reset $treeish -- $path" should be usable on
+        * any tree-ish, this is not strictly correct. We are not
+        * moving the HEAD to any commit; we are merely resetting the
+        * entries in the index to that of a treeish.
+        */
        commit = lookup_commit_reference(sha1);
        if (!commit)
                die(_("Could not parse object '%s'."), rev);
index 13495b88f5da1efc2094c0e69abfe93605ee8c03..32788a9f86427237d0f4838362c1e3bc722fa258 100644 (file)
@@ -195,6 +195,12 @@ static int anti_reference(const char *refname, const unsigned char *sha1, int fl
        return 0;
 }
 
+static int show_abbrev(const unsigned char *sha1, void *cb_data)
+{
+       show_rev(NORMAL, sha1, NULL);
+       return 0;
+}
+
 static void show_datestring(const char *flag, const char *datestr)
 {
        static char buffer[100];
@@ -238,7 +244,7 @@ static int try_difference(const char *arg)
                next = "HEAD";
        if (dotdot == arg)
                this = "HEAD";
-       if (!get_sha1(this, sha1) && !get_sha1(next, end)) {
+       if (!get_sha1_committish(this, sha1) && !get_sha1_committish(next, end)) {
                show_rev(NORMAL, end, next);
                show_rev(symmetric ? NORMAL : REVERSED, sha1, this);
                if (symmetric) {
@@ -278,7 +284,7 @@ static int try_parent_shorthands(const char *arg)
                return 0;
 
        *dotdot = 0;
-       if (get_sha1(arg, sha1))
+       if (get_sha1_committish(arg, sha1))
                return 0;
 
        if (!parents_only)
@@ -589,6 +595,10 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
                                for_each_ref(show_reference, NULL);
                                continue;
                        }
+                       if (!prefixcmp(arg, "--disambiguate=")) {
+                               for_each_abbrev(arg + 15, show_abbrev, NULL);
+                               continue;
+                       }
                        if (!strcmp(arg, "--bisect")) {
                                for_each_ref_in("refs/bisect/bad", show_reference, NULL);
                                for_each_ref_in("refs/bisect/good", anti_reference, NULL);
diff --git a/cache.h b/cache.h
index 6a1aff5e2aa0cbbdc6f1cb49425f45421b2ea18f..2997b918e8201516fe4df91f7cc3fbf8ee2253e4 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -790,17 +790,25 @@ struct object_context {
        unsigned mode;
 };
 
+#define GET_SHA1_QUIETLY        01
+#define GET_SHA1_COMMIT         02
+#define GET_SHA1_COMMITTISH     04
+#define GET_SHA1_TREE          010
+#define GET_SHA1_TREEISH       020
+#define GET_SHA1_BLOB         040
+#define GET_SHA1_ONLY_TO_DIE 04000
+
 extern int get_sha1(const char *str, unsigned char *sha1);
-extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, int only_to_die, const char *prefix);
-static inline int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode)
-{
-       return get_sha1_with_mode_1(str, sha1, mode, 0, NULL);
-}
-extern int get_sha1_with_context_1(const char *name, unsigned char *sha1, struct object_context *orc, int only_to_die, const char *prefix);
-static inline int get_sha1_with_context(const char *str, unsigned char *sha1, struct object_context *orc)
-{
-       return get_sha1_with_context_1(str, sha1, orc, 0, NULL);
-}
+extern int get_sha1_commit(const char *str, unsigned char *sha1);
+extern int get_sha1_committish(const char *str, unsigned char *sha1);
+extern int get_sha1_tree(const char *str, unsigned char *sha1);
+extern int get_sha1_treeish(const char *str, unsigned char *sha1);
+extern int get_sha1_blob(const char *str, unsigned char *sha1);
+extern void maybe_die_on_misspelt_object_name(const char *name, const char *prefix);
+extern int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc);
+
+typedef int each_abbrev_fn(const unsigned char *sha1, void *);
+extern int for_each_abbrev(const char *prefix, each_abbrev_fn, void *);
 
 /*
  * Try to read a SHA1 in hexadecimal format from the 40 characters
index 8248a994a50ab91874600567e544aa3735e4aa98..42af4c1f238b96eeb9e88b227b6f6c10ef317058 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -68,7 +68,7 @@ struct commit *lookup_commit_reference_by_name(const char *name)
        unsigned char sha1[20];
        struct commit *commit;
 
-       if (get_sha1(name, sha1))
+       if (get_sha1_committish(name, sha1))
                return NULL;
        commit = lookup_commit_reference(sha1);
        if (!commit || parse_commit(commit))
index 5b81a92e3ac65ab0295f25198511fc83b4bbf1c9..c64bf68fa1f84a226cec97ddaf1970cf0aaa308b 100644 (file)
@@ -1000,7 +1000,7 @@ static int add_parents_only(struct rev_info *revs, const char *arg_, int flags)
                flags ^= UNINTERESTING;
                arg++;
        }
-       if (get_sha1(arg, sha1))
+       if (get_sha1_committish(arg, sha1))
                return 0;
        while (1) {
                it = get_reference(revs, arg, sha1, 0);
@@ -1114,16 +1114,16 @@ static void prepare_show_merge(struct rev_info *revs)
        revs->limited = 1;
 }
 
-int handle_revision_arg(const char *arg_, struct rev_info *revs,
-                       int flags,
-                       int cant_be_filename)
+int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsigned revarg_opt)
 {
-       unsigned mode;
+       struct object_context oc;
        char *dotdot;
        struct object *object;
        unsigned char sha1[20];
        int local_flags;
        const char *arg = arg_;
+       int cant_be_filename = revarg_opt & REVARG_CANNOT_BE_FILENAME;
+       unsigned get_sha1_flags = 0;
 
        dotdot = strstr(arg, "..");
        if (dotdot) {
@@ -1141,8 +1141,8 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs,
                        next = "HEAD";
                if (dotdot == arg)
                        this = "HEAD";
-               if (!get_sha1(this, from_sha1) &&
-                   !get_sha1(next, sha1)) {
+               if (!get_sha1_committish(this, from_sha1) &&
+                   !get_sha1_committish(next, sha1)) {
                        struct commit *a, *b;
                        struct commit_list *exclude;
 
@@ -1201,13 +1201,17 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs,
                local_flags = UNINTERESTING;
                arg++;
        }
-       if (get_sha1_with_mode(arg, sha1, &mode))
+
+       if (revarg_opt & REVARG_COMMITTISH)
+               get_sha1_flags = GET_SHA1_COMMITTISH;
+
+       if (get_sha1_with_context(arg, get_sha1_flags, sha1, &oc))
                return revs->ignore_missing ? 0 : -1;
        if (!cant_be_filename)
                verify_non_filename(revs->prefix, arg);
        object = get_reference(revs, arg, sha1, flags ^ local_flags);
        add_rev_cmdline(revs, object, arg_, REV_CMD_REV, flags ^ local_flags);
-       add_pending_object_with_mode(revs, object, arg, mode);
+       add_pending_object_with_mode(revs, object, arg, oc.mode);
        return 0;
 }
 
@@ -1257,7 +1261,7 @@ static void read_revisions_from_stdin(struct rev_info *revs,
                        }
                        die("options not supported in --stdin mode");
                }
-               if (handle_revision_arg(sb.buf, revs, 0, 1))
+               if (handle_revision_arg(sb.buf, revs, 0, REVARG_CANNOT_BE_FILENAME))
                        die("bad revision '%s'", sb.buf);
        }
        if (seen_dashdash)
@@ -1708,7 +1712,7 @@ static int handle_revision_pseudo_opt(const char *submodule,
  */
 int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct setup_revision_opt *opt)
 {
-       int i, flags, left, seen_dashdash, read_from_stdin, got_rev_arg = 0;
+       int i, flags, left, seen_dashdash, read_from_stdin, got_rev_arg = 0, revarg_opt;
        struct cmdline_pathspec prune_data;
        const char *submodule = NULL;
 
@@ -1736,6 +1740,9 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 
        /* Second, deal with arguments and options */
        flags = 0;
+       revarg_opt = opt ? opt->revarg_opt : 0;
+       if (seen_dashdash)
+               revarg_opt |= REVARG_CANNOT_BE_FILENAME;
        read_from_stdin = 0;
        for (left = i = 1; i < argc; i++) {
                const char *arg = argv[i];
@@ -1771,7 +1778,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
                        continue;
                }
 
-               if (handle_revision_arg(arg, revs, flags, seen_dashdash)) {
+
+               if (handle_revision_arg(arg, revs, flags, revarg_opt)) {
                        int j;
                        if (seen_dashdash || *arg == '^')
                                die("bad revision '%s'", arg);
@@ -1822,11 +1830,11 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
        if (revs->def && !revs->pending.nr && !got_rev_arg) {
                unsigned char sha1[20];
                struct object *object;
-               unsigned mode;
-               if (get_sha1_with_mode(revs->def, sha1, &mode))
+               struct object_context oc;
+               if (get_sha1_with_context(revs->def, 0, sha1, &oc))
                        die("bad default revision '%s'", revs->def);
                object = get_reference(revs, revs->def, sha1, 0);
-               add_pending_object_with_mode(revs, object, revs->def, mode);
+               add_pending_object_with_mode(revs, object, revs->def, oc.mode);
        }
 
        /* Did the user ask for any diff output? Run the diff! */
index 863f4f64543bd9f9e830e7c9567def23e906c7d9..cb5ab3513bc9982095e292119b9119d333556256 100644 (file)
@@ -184,6 +184,7 @@ struct setup_revision_opt {
        void (*tweak)(struct rev_info *, struct setup_revision_opt *);
        const char *submodule;
        int assume_dashdash;
+       unsigned revarg_opt;
 };
 
 extern void init_revisions(struct rev_info *revs, const char *prefix);
@@ -191,7 +192,9 @@ extern int setup_revisions(int argc, const char **argv, struct rev_info *revs, s
 extern void parse_revision_opt(struct rev_info *revs, struct parse_opt_ctx_t *ctx,
                                 const struct option *options,
                                 const char * const usagestr[]);
-extern int handle_revision_arg(const char *arg, struct rev_info *revs,int flags,int cant_be_filename);
+#define REVARG_CANNOT_BE_FILENAME 01
+#define REVARG_COMMITTISH 02
+extern int handle_revision_arg(const char *arg, struct rev_info *revs, int flags, unsigned revarg_opt);
 
 extern void reset_revision_walk(void);
 extern int prepare_revision_walk(struct rev_info *revs);
diff --git a/setup.c b/setup.c
index e11497720e01dd14a66e152883e675669fc3b548..9139beefc75c4fe92cf8c7dc54a9fae972995aca 100644 (file)
--- a/setup.c
+++ b/setup.c
@@ -77,9 +77,6 @@ static void NORETURN die_verify_filename(const char *prefix,
                                         const char *arg,
                                         int diagnose_misspelt_rev)
 {
-       unsigned char sha1[20];
-       unsigned mode;
-
        if (!diagnose_misspelt_rev)
                die("%s: no such path in the working tree.\n"
                    "Use '-- <path>...' to specify paths that do not exist locally.",
@@ -88,11 +85,10 @@ static void NORETURN die_verify_filename(const char *prefix,
         * Saying "'(icase)foo' does not exist in the index" when the
         * user gave us ":(icase)foo" is just stupid.  A magic pathspec
         * begins with a colon and is followed by a non-alnum; do not
-        * let get_sha1_with_mode_1(only_to_die=1) to even trigger.
+        * let maybe_die_on_misspelt_object_name() even trigger.
         */
        if (!(arg[0] == ':' && !isalnum(arg[1])))
-               /* try a detailed diagnostic ... */
-               get_sha1_with_mode_1(arg, sha1, &mode, 1, prefix);
+               maybe_die_on_misspelt_object_name(arg, prefix);
 
        /* ... or fall back the most general message. */
        die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
index 5d81ea0564c8d90b417eb8ec5ed8c32baa2c3ea3..95003c77ea9a0ee240d60bc7958bb48245b14ad4 100644 (file)
@@ -9,14 +9,82 @@
 
 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
 
-static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
+typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
+
+struct disambiguate_state {
+       disambiguate_hint_fn fn;
+       void *cb_data;
+       unsigned char candidate[20];
+       unsigned candidate_exists:1;
+       unsigned candidate_checked:1;
+       unsigned candidate_ok:1;
+       unsigned disambiguate_fn_used:1;
+       unsigned ambiguous:1;
+       unsigned always_call_fn:1;
+};
+
+static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
+{
+       if (ds->always_call_fn) {
+               ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
+               return;
+       }
+       if (!ds->candidate_exists) {
+               /* this is the first candidate */
+               hashcpy(ds->candidate, current);
+               ds->candidate_exists = 1;
+               return;
+       } else if (!hashcmp(ds->candidate, current)) {
+               /* the same as what we already have seen */
+               return;
+       }
+
+       if (!ds->fn) {
+               /* cannot disambiguate between ds->candidate and current */
+               ds->ambiguous = 1;
+               return;
+       }
+
+       if (!ds->candidate_checked) {
+               ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
+               ds->disambiguate_fn_used = 1;
+               ds->candidate_checked = 1;
+       }
+
+       if (!ds->candidate_ok) {
+               /* discard the candidate; we know it does not satisify fn */
+               hashcpy(ds->candidate, current);
+               ds->candidate_checked = 0;
+               return;
+       }
+
+       /* if we reach this point, we know ds->candidate satisfies fn */
+       if (ds->fn(current, ds->cb_data)) {
+               /*
+                * if both current and candidate satisfy fn, we cannot
+                * disambiguate.
+                */
+               ds->candidate_ok = 0;
+               ds->ambiguous = 1;
+       }
+
+       /* otherwise, current can be discarded and candidate is still good */
+}
+
+static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
 {
        struct alternate_object_database *alt;
        char hex[40];
-       int found = 0;
        static struct alternate_object_database *fakeent;
 
        if (!fakeent) {
+               /*
+                * Create a "fake" alternate object database that
+                * points to our own object database, to make it
+                * easier to get a temporary working space in
+                * alt->name/alt->base while iterating over the
+                * object databases including our own.
+                */
                const char *objdir = get_object_directory();
                int objdir_len = strlen(objdir);
                int entlen = objdir_len + 43;
@@ -27,33 +95,28 @@ static int find_short_object_filename(int len, const char *name, unsigned char *
        }
        fakeent->next = alt_odb_list;
 
-       sprintf(hex, "%.2s", name);
-       for (alt = fakeent; alt && found < 2; alt = alt->next) {
+       sprintf(hex, "%.2s", hex_pfx);
+       for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
                struct dirent *de;
                DIR *dir;
-               sprintf(alt->name, "%.2s/", name);
+               sprintf(alt->name, "%.2s/", hex_pfx);
                dir = opendir(alt->base);
                if (!dir)
                        continue;
-               while ((de = readdir(dir)) != NULL) {
+
+               while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
+                       unsigned char sha1[20];
+
                        if (strlen(de->d_name) != 38)
                                continue;
-                       if (memcmp(de->d_name, name + 2, len - 2))
+                       if (memcmp(de->d_name, hex_pfx + 2, len - 2))
                                continue;
-                       if (!found) {
-                               memcpy(hex + 2, de->d_name, 38);
-                               found++;
-                       }
-                       else if (memcmp(hex + 2, de->d_name, 38)) {
-                               found = 2;
-                               break;
-                       }
+                       memcpy(hex + 2, de->d_name, 38);
+                       if (!get_sha1_hex(hex, sha1))
+                               update_candidates(ds, sha1);
                }
                closedir(dir);
        }
-       if (found == 1)
-               return get_sha1_hex(hex, sha1) == 0;
-       return found;
 }
 
 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
@@ -71,103 +134,157 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
        return 1;
 }
 
-static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
+static void unique_in_pack(int len,
+                         const unsigned char *bin_pfx,
+                          struct packed_git *p,
+                          struct disambiguate_state *ds)
 {
-       struct packed_git *p;
-       const unsigned char *found_sha1 = NULL;
-       int found = 0;
-
-       prepare_packed_git();
-       for (p = packed_git; p && found < 2; p = p->next) {
-               uint32_t num, last;
-               uint32_t first = 0;
-               open_pack_index(p);
-               num = p->num_objects;
-               last = num;
-               while (first < last) {
-                       uint32_t mid = (first + last) / 2;
-                       const unsigned char *now;
-                       int cmp;
-
-                       now = nth_packed_object_sha1(p, mid);
-                       cmp = hashcmp(match, now);
-                       if (!cmp) {
-                               first = mid;
-                               break;
-                       }
-                       if (cmp > 0) {
-                               first = mid+1;
-                               continue;
-                       }
-                       last = mid;
+       uint32_t num, last, i, first = 0;
+       const unsigned char *current = NULL;
+
+       open_pack_index(p);
+       num = p->num_objects;
+       last = num;
+       while (first < last) {
+               uint32_t mid = (first + last) / 2;
+               const unsigned char *current;
+               int cmp;
+
+               current = nth_packed_object_sha1(p, mid);
+               cmp = hashcmp(bin_pfx, current);
+               if (!cmp) {
+                       first = mid;
+                       break;
                }
-               if (first < num) {
-                       const unsigned char *now, *next;
-                      now = nth_packed_object_sha1(p, first);
-                       if (match_sha(len, match, now)) {
-                               next = nth_packed_object_sha1(p, first+1);
-                              if (!next|| !match_sha(len, match, next)) {
-                                       /* unique within this pack */
-                                       if (!found) {
-                                               found_sha1 = now;
-                                               found++;
-                                       }
-                                       else if (hashcmp(found_sha1, now)) {
-                                               found = 2;
-                                               break;
-                                       }
-                               }
-                               else {
-                                       /* not even unique within this pack */
-                                       found = 2;
-                                       break;
-                               }
-                       }
+               if (cmp > 0) {
+                       first = mid+1;
+                       continue;
                }
+               last = mid;
+       }
+
+       /*
+        * At this point, "first" is the location of the lowest object
+        * with an object name that could match "bin_pfx".  See if we have
+        * 0, 1 or more objects that actually match(es).
+        */
+       for (i = first; i < num && !ds->ambiguous; i++) {
+               current = nth_packed_object_sha1(p, i);
+               if (!match_sha(len, bin_pfx, current))
+                       break;
+               update_candidates(ds, current);
        }
-       if (found == 1)
-               hashcpy(sha1, found_sha1);
-       return found;
+}
+
+static void find_short_packed_object(int len, const unsigned char *bin_pfx,
+                                    struct disambiguate_state *ds)
+{
+       struct packed_git *p;
+
+       prepare_packed_git();
+       for (p = packed_git; p && !ds->ambiguous; p = p->next)
+               unique_in_pack(len, bin_pfx, p, ds);
 }
 
 #define SHORT_NAME_NOT_FOUND (-1)
 #define SHORT_NAME_AMBIGUOUS (-2)
 
-static int find_unique_short_object(int len, char *canonical,
-                                   unsigned char *res, unsigned char *sha1)
+static int finish_object_disambiguation(struct disambiguate_state *ds,
+                                       unsigned char *sha1)
 {
-       int has_unpacked, has_packed;
-       unsigned char unpacked_sha1[20], packed_sha1[20];
+       if (ds->ambiguous)
+               return SHORT_NAME_AMBIGUOUS;
 
-       prepare_alt_odb();
-       has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
-       has_packed = find_short_packed_object(len, res, packed_sha1);
-       if (!has_unpacked && !has_packed)
+       if (!ds->candidate_exists)
                return SHORT_NAME_NOT_FOUND;
-       if (1 < has_unpacked || 1 < has_packed)
+
+       if (!ds->candidate_checked)
+               /*
+                * If this is the only candidate, there is no point
+                * calling the disambiguation hint callback.
+                *
+                * On the other hand, if the current candidate
+                * replaced an earlier candidate that did _not_ pass
+                * the disambiguation hint callback, then we do have
+                * more than one objects that match the short name
+                * given, so we should make sure this one matches;
+                * otherwise, if we discovered this one and the one
+                * that we previously discarded in the reverse order,
+                * we would end up showing different results in the
+                * same repository!
+                */
+               ds->candidate_ok = (!ds->disambiguate_fn_used ||
+                                   ds->fn(ds->candidate, ds->cb_data));
+
+       if (!ds->candidate_ok)
                return SHORT_NAME_AMBIGUOUS;
-       if (has_unpacked != has_packed) {
-               hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
+
+       hashcpy(sha1, ds->candidate);
+       return 0;
+}
+
+static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
+{
+       int kind = sha1_object_info(sha1, NULL);
+       return kind == OBJ_COMMIT;
+}
+
+static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
+{
+       struct object *obj;
+       int kind;
+
+       kind = sha1_object_info(sha1, NULL);
+       if (kind == OBJ_COMMIT)
+               return 1;
+       if (kind != OBJ_TAG)
                return 0;
-       }
-       /* Both have unique ones -- do they match? */
-       if (hashcmp(packed_sha1, unpacked_sha1))
-               return SHORT_NAME_AMBIGUOUS;
-       hashcpy(sha1, packed_sha1);
+
+       /* We need to do this the hard way... */
+       obj = deref_tag(lookup_object(sha1), NULL, 0);
+       if (obj && obj->type == OBJ_COMMIT)
+               return 1;
        return 0;
 }
 
-static int get_short_sha1(const char *name, int len, unsigned char *sha1,
-                         int quietly)
+static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
 {
-       int i, status;
-       char canonical[40];
-       unsigned char res[20];
+       int kind = sha1_object_info(sha1, NULL);
+       return kind == OBJ_TREE;
+}
 
-       if (len < MINIMUM_ABBREV || len > 40)
-               return -1;
-       hashclr(res);
-       memset(canonical, 'x', 40);
+static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
+{
+       struct object *obj;
+       int kind;
+
+       kind = sha1_object_info(sha1, NULL);
+       if (kind == OBJ_TREE || kind == OBJ_COMMIT)
+               return 1;
+       if (kind != OBJ_TAG)
+               return 0;
+
+       /* We need to do this the hard way... */
+       obj = deref_tag(lookup_object(sha1), NULL, 0);
+       if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
+               return 1;
+       return 0;
+}
+
+static int disambiguate_blob_only(const unsigned char *sha1, void *cb_data_unused)
+{
+       int kind = sha1_object_info(sha1, NULL);
+       return kind == OBJ_BLOB;
+}
+
+static int prepare_prefixes(const char *name, int len,
+                           unsigned char *bin_pfx,
+                           char *hex_pfx)
+{
+       int i;
+
+       hashclr(bin_pfx);
+       memset(hex_pfx, 'x', 40);
        for (i = 0; i < len ;i++) {
                unsigned char c = name[i];
                unsigned char val;
@@ -181,18 +298,76 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
                }
                else
                        return -1;
-               canonical[i] = c;
+               hex_pfx[i] = c;
                if (!(i & 1))
                        val <<= 4;
-               res[i >> 1] |= val;
+               bin_pfx[i >> 1] |= val;
        }
+       return 0;
+}
+
+static int get_short_sha1(const char *name, int len, unsigned char *sha1,
+                         unsigned flags)
+{
+       int status;
+       char hex_pfx[40];
+       unsigned char bin_pfx[20];
+       struct disambiguate_state ds;
+       int quietly = !!(flags & GET_SHA1_QUIETLY);
+
+       if (len < MINIMUM_ABBREV || len > 40)
+               return -1;
+       if (prepare_prefixes(name, len, bin_pfx, hex_pfx) < 0)
+               return -1;
+
+       prepare_alt_odb();
+
+       memset(&ds, 0, sizeof(ds));
+       if (flags & GET_SHA1_COMMIT)
+               ds.fn = disambiguate_commit_only;
+       else if (flags & GET_SHA1_COMMITTISH)
+               ds.fn = disambiguate_committish_only;
+       else if (flags & GET_SHA1_TREE)
+               ds.fn = disambiguate_tree_only;
+       else if (flags & GET_SHA1_TREEISH)
+               ds.fn = disambiguate_treeish_only;
+       else if (flags & GET_SHA1_BLOB)
+               ds.fn = disambiguate_blob_only;
+
+       find_short_object_filename(len, hex_pfx, &ds);
+       find_short_packed_object(len, bin_pfx, &ds);
+       status = finish_object_disambiguation(&ds, sha1);
 
-       status = find_unique_short_object(i, canonical, res, sha1);
        if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
-               return error("short SHA1 %.*s is ambiguous.", len, canonical);
+               return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
        return status;
 }
 
+
+int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
+{
+       char hex_pfx[40];
+       unsigned char bin_pfx[20];
+       struct disambiguate_state ds;
+       int len = strlen(prefix);
+
+       if (len < MINIMUM_ABBREV || len > 40)
+               return -1;
+       if (prepare_prefixes(prefix, len, bin_pfx, hex_pfx) < 0)
+               return -1;
+
+       prepare_alt_odb();
+
+       memset(&ds, 0, sizeof(ds));
+       ds.always_call_fn = 1;
+       ds.cb_data = cb_data;
+       ds.fn = fn;
+
+       find_short_object_filename(len, hex_pfx, &ds);
+       find_short_packed_object(len, bin_pfx, &ds);
+       return ds.ambiguous;
+}
+
 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 {
        int status, exists;
@@ -204,7 +379,7 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len)
                return hex;
        while (len < 40) {
                unsigned char sha1_ret[20];
-               status = get_short_sha1(hex, len, sha1_ret, 1);
+               status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
                if (exists
                    ? !status
                    : status == SHORT_NAME_NOT_FOUND) {
@@ -255,7 +430,7 @@ static inline int upstream_mark(const char *string, int len)
        return 0;
 }
 
-static int get_sha1_1(const char *name, int len, unsigned char *sha1);
+static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 {
@@ -292,7 +467,7 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
                ret = interpret_branch_name(str+at, &buf);
                if (ret > 0) {
                        /* substitute this branch name and restart */
-                       return get_sha1_1(buf.buf, buf.len, sha1);
+                       return get_sha1_1(buf.buf, buf.len, sha1, 0);
                } else if (ret == 0) {
                        return -1;
                }
@@ -362,7 +537,7 @@ static int get_parent(const char *name, int len,
                      unsigned char *result, int idx)
 {
        unsigned char sha1[20];
-       int ret = get_sha1_1(name, len, sha1);
+       int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
        struct commit *commit;
        struct commit_list *p;
 
@@ -395,7 +570,7 @@ static int get_nth_ancestor(const char *name, int len,
        struct commit *commit;
        int ret;
 
-       ret = get_sha1_1(name, len, sha1);
+       ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
        if (ret)
                return ret;
        commit = lookup_commit_reference(sha1);
@@ -441,6 +616,7 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
        unsigned char outer[20];
        const char *sp;
        unsigned int expected_type = 0;
+       unsigned lookup_flags = 0;
        struct object *o;
 
        /*
@@ -476,7 +652,10 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
        else
                return -1;
 
-       if (get_sha1_1(name, sp - name - 2, outer))
+       if (expected_type == OBJ_COMMIT)
+               lookup_flags = GET_SHA1_COMMITTISH;
+
+       if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
                return -1;
 
        o = parse_object(outer);
@@ -525,6 +704,7 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 {
        const char *cp;
+       unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 
        for (cp = name + len - 1; name + 2 <= cp; cp--) {
                char ch = *cp;
@@ -535,14 +715,14 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
                        if (ch == 'g' && cp[-1] == '-') {
                                cp++;
                                len -= cp - name;
-                               return get_short_sha1(cp, len, sha1, 1);
+                               return get_short_sha1(cp, len, sha1, flags);
                        }
                }
        }
        return -1;
 }
 
-static int get_sha1_1(const char *name, int len, unsigned char *sha1)
+static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
 {
        int ret, has_suffix;
        const char *cp;
@@ -587,7 +767,7 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1)
        if (!ret)
                return 0;
 
-       return get_short_sha1(name, len, sha1, 0);
+       return get_short_sha1(name, len, sha1, lookup_flags);
 }
 
 /*
@@ -769,7 +949,7 @@ int get_sha1_mb(const char *name, unsigned char *sha1)
                struct strbuf sb;
                strbuf_init(&sb, dots - name);
                strbuf_add(&sb, name, dots - name);
-               st = get_sha1(sb.buf, sha1_tmp);
+               st = get_sha1_committish(sb.buf, sha1_tmp);
                strbuf_release(&sb);
        }
        if (st)
@@ -778,7 +958,7 @@ int get_sha1_mb(const char *name, unsigned char *sha1)
        if (!one)
                return -1;
 
-       if (get_sha1(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
+       if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
                return -1;
        two = lookup_commit_reference_gently(sha1_tmp, 0);
        if (!two)
@@ -905,7 +1085,52 @@ int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
 int get_sha1(const char *name, unsigned char *sha1)
 {
        struct object_context unused;
-       return get_sha1_with_context(name, sha1, &unused);
+       return get_sha1_with_context(name, 0, sha1, &unused);
+}
+
+/*
+ * Many callers know that the user meant to name a committish by
+ * syntactical positions where the object name appears.  Calling this
+ * function allows the machinery to disambiguate shorter-than-unique
+ * abbreviated object names between committish and others.
+ *
+ * Note that this does NOT error out when the named object is not a
+ * committish. It is merely to give a hint to the disambiguation
+ * machinery.
+ */
+int get_sha1_committish(const char *name, unsigned char *sha1)
+{
+       struct object_context unused;
+       return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
+                                    sha1, &unused);
+}
+
+int get_sha1_treeish(const char *name, unsigned char *sha1)
+{
+       struct object_context unused;
+       return get_sha1_with_context(name, GET_SHA1_TREEISH,
+                                    sha1, &unused);
+}
+
+int get_sha1_commit(const char *name, unsigned char *sha1)
+{
+       struct object_context unused;
+       return get_sha1_with_context(name, GET_SHA1_COMMIT,
+                                    sha1, &unused);
+}
+
+int get_sha1_tree(const char *name, unsigned char *sha1)
+{
+       struct object_context unused;
+       return get_sha1_with_context(name, GET_SHA1_TREE,
+                                    sha1, &unused);
+}
+
+int get_sha1_blob(const char *name, unsigned char *sha1)
+{
+       struct object_context unused;
+       return get_sha1_with_context(name, GET_SHA1_BLOB,
+                                    sha1, &unused);
 }
 
 /* Must be called only when object_name:filename doesn't exist. */
@@ -1004,16 +1229,6 @@ static void diagnose_invalid_index_path(int stage,
 }
 
 
-int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode,
-                        int only_to_die, const char *prefix)
-{
-       struct object_context oc;
-       int ret;
-       ret = get_sha1_with_context_1(name, sha1, &oc, only_to_die, prefix);
-       *mode = oc.mode;
-       return ret;
-}
-
 static char *resolve_relative_path(const char *rel)
 {
        if (prefixcmp(rel, "./") && prefixcmp(rel, "../"))
@@ -1031,20 +1246,24 @@ static char *resolve_relative_path(const char *rel)
                           rel);
 }
 
-int get_sha1_with_context_1(const char *name, unsigned char *sha1,
-                           struct object_context *oc,
-                           int only_to_die, const char *prefix)
+static int get_sha1_with_context_1(const char *name,
+                                  unsigned flags,
+                                  const char *prefix,
+                                  unsigned char *sha1,
+                                  struct object_context *oc)
 {
        int ret, bracket_depth;
        int namelen = strlen(name);
        const char *cp;
+       int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
 
        memset(oc, 0, sizeof(*oc));
        oc->mode = S_IFINVALID;
-       ret = get_sha1_1(name, namelen, sha1);
+       ret = get_sha1_1(name, namelen, sha1, flags);
        if (!ret)
                return ret;
-       /* sha1:path --> object name of path in ent sha1
+       /*
+        * sha1:path --> object name of path in ent sha1
         * :path -> object name of absolute path in index
         * :./path -> object name of path relative to cwd in index
         * :[0-3]:path -> object name of path in index at stage
@@ -1119,7 +1338,7 @@ int get_sha1_with_context_1(const char *name, unsigned char *sha1,
                        strncpy(object_name, name, cp-name);
                        object_name[cp-name] = '\0';
                }
-               if (!get_sha1_1(name, cp-name, tree_sha1)) {
+               if (!get_sha1_1(name, cp-name, tree_sha1, GET_SHA1_TREEISH)) {
                        const char *filename = cp+1;
                        char *new_filename = NULL;
 
@@ -1146,3 +1365,22 @@ int get_sha1_with_context_1(const char *name, unsigned char *sha1,
        }
        return ret;
 }
+
+/*
+ * Call this function when you know "name" given by the end user must
+ * name an object but it doesn't; the function _may_ die with a better
+ * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
+ * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
+ * you have a chance to diagnose the error further.
+ */
+void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
+{
+       struct object_context oc;
+       unsigned char sha1[20];
+       get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
+}
+
+int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
+{
+       return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
+}
diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
new file mode 100755 (executable)
index 0000000..6b3d797
--- /dev/null
@@ -0,0 +1,264 @@
+#!/bin/sh
+
+test_description='object name disambiguation
+
+Create blobs, trees, commits and a tag that all share the same
+prefix, and make sure "git rev-parse" can take advantage of
+type information to disambiguate short object names that are
+not necessarily unique.
+
+The final history used in the test has five commits, with the bottom
+one tagged as v1.0.0.  They all have one regular file each.
+
+  +-------------------------------------------+
+  |                                           |
+  |           .-------b3wettvi---- ad2uee     |
+  |          /                   /            |
+  |  a2onsxbvj---czy8f73t--ioiley5o           |
+  |                                           |
+  +-------------------------------------------+
+
+'
+
+. ./test-lib.sh
+
+test_expect_success 'blob and tree' '
+       test_tick &&
+       (
+               for i in 0 1 2 3 4 5 6 7 8 9
+               do
+                       echo $i
+               done
+               echo
+               echo b1rwzyc3
+       ) >a0blgqsjc &&
+
+       # create one blob 0000000000b36
+       git add a0blgqsjc &&
+
+       # create one tree 0000000000cdc
+       git write-tree
+'
+
+test_expect_success 'warn ambiguity when no candidate matches type hint' '
+       test_must_fail git rev-parse --verify 000000000^{commit} 2>actual &&
+       grep "short SHA1 000000000 is ambiguous" actual
+'
+
+test_expect_success 'disambiguate tree-ish' '
+       # feed tree-ish in an unambiguous way
+       git rev-parse --verify 0000000000cdc:a0blgqsjc &&
+
+       # ambiguous at the object name level, but there is only one
+       # such tree-ish (the other is a blob)
+       git rev-parse --verify 000000000:a0blgqsjc
+'
+
+test_expect_success 'disambiguate blob' '
+       sed -e "s/|$//" >patch <<-EOF &&
+       diff --git a/frotz b/frotz
+       index 000000000..ffffff 100644
+       --- a/frotz
+       +++ b/frotz
+       @@ -10,3 +10,4 @@
+        9
+        |
+        b1rwzyc3
+       +irwry
+       EOF
+       (
+               GIT_INDEX_FILE=frotz &&
+               export GIT_INDEX_FILE &&
+               git apply --build-fake-ancestor frotz patch &&
+               git cat-file blob :frotz >actual
+       ) &&
+       test_cmp a0blgqsjc actual
+'
+
+test_expect_success 'disambiguate tree' '
+       commit=$(echo "d7xm" | git commit-tree 000000000) &&
+       test $(git rev-parse $commit^{tree}) = $(git rev-parse 0000000000cdc)
+'
+
+test_expect_success 'first commit' '
+       # create one commit 0000000000e4f
+       git commit -m a2onsxbvj
+'
+
+test_expect_success 'disambiguate commit-ish' '
+       # feed commit-ish in an unambiguous way
+       git rev-parse --verify 0000000000e4f^{commit} &&
+
+       # ambiguous at the object name level, but there is only one
+       # such commit (the others are tree and blob)
+       git rev-parse --verify 000000000^{commit} &&
+
+       # likewise
+       git rev-parse --verify 000000000^0
+'
+
+test_expect_success 'disambiguate commit' '
+       commit=$(echo "hoaxj" | git commit-tree 0000000000cdc -p 000000000) &&
+       test $(git rev-parse $commit^) = $(git rev-parse 0000000000e4f)
+'
+
+test_expect_success 'log name1..name2 takes only commit-ishes on both ends' '
+       git log 000000000..000000000 &&
+       git log ..000000000 &&
+       git log 000000000.. &&
+       git log 000000000...000000000 &&
+       git log ...000000000 &&
+       git log 000000000...
+'
+
+test_expect_success 'rev-parse name1..name2 takes only commit-ishes on both ends' '
+       git rev-parse 000000000..000000000 &&
+       git rev-parse ..000000000 &&
+       git rev-parse 000000000..
+'
+
+test_expect_success 'git log takes only commit-ish' '
+       git log 000000000
+'
+
+test_expect_success 'git reset takes only commit-ish' '
+       git reset 000000000
+'
+
+test_expect_success 'first tag' '
+       # create one tag 0000000000f8f
+       git tag -a -m j7cp83um v1.0.0
+'
+
+test_expect_failure 'two semi-ambiguous commit-ish' '
+       # Once the parser becomes ultra-smart, it could notice that
+       # 110282 before ^{commit} name many different objects, but
+       # that only two (HEAD and v1.0.0 tag) can be peeled to commit,
+       # and that peeling them down to commit yield the same commit
+       # without ambiguity.
+       git rev-parse --verify 110282^{commit} &&
+
+       # likewise
+       git log 000000000..000000000 &&
+       git log ..000000000 &&
+       git log 000000000.. &&
+       git log 000000000...000000000 &&
+       git log ...000000000 &&
+       git log 000000000...
+'
+
+test_expect_failure 'three semi-ambiguous tree-ish' '
+       # Likewise for tree-ish.  HEAD, v1.0.0 and HEAD^{tree} share
+       # the prefix but peeling them to tree yields the same thing
+       git rev-parse --verify 000000000^{tree}
+'
+
+test_expect_success 'parse describe name' '
+       # feed an unambiguous describe name
+       git rev-parse --verify v1.0.0-0-g0000000000e4f &&
+
+       # ambiguous at the object name level, but there is only one
+       # such commit (others are blob, tree and tag)
+       git rev-parse --verify v1.0.0-0-g000000000
+'
+
+test_expect_success 'more history' '
+       # commit 0000000000043
+       git mv a0blgqsjc d12cr3h8t &&
+       echo h62xsjeu >>d12cr3h8t &&
+       git add d12cr3h8t &&
+
+       test_tick &&
+       git commit -m czy8f73t &&
+
+       # commit 00000000008ec
+       git mv d12cr3h8t j000jmpzn &&
+       echo j08bekfvt >>j000jmpzn &&
+       git add j000jmpzn &&
+
+       test_tick &&
+       git commit -m ioiley5o &&
+
+       # commit 0000000005b0
+       git checkout v1.0.0^0 &&
+       git mv a0blgqsjc f5518nwu &&
+
+       for i in h62xsjeu j08bekfvt kg7xflhm
+       do
+               echo $i
+       done >>f5518nwu &&
+       git add f5518nwu &&
+
+       test_tick &&
+       git commit -m b3wettvi &&
+       side=$(git rev-parse HEAD) &&
+
+       # commit 000000000066
+       git checkout master &&
+
+       # If you use recursive, merge will fail and you will need to
+       # clean up a0blgqsjc as well.  If you use resolve, merge will
+       # succeed.
+       test_might_fail git merge --no-commit -s recursive $side &&
+       git rm -f f5518nwu j000jmpzn &&
+
+       test_might_fail git rm -f a0blgqsjc &&
+       (
+               git cat-file blob $side:f5518nwu
+               echo j3l0i9s6
+       ) >ab2gs879 &&
+       git add ab2gs879 &&
+
+       test_tick &&
+       git commit -m ad2uee
+
+'
+
+test_expect_failure 'parse describe name taking advantage of generation' '
+       # ambiguous at the object name level, but there is only one
+       # such commit at generation 0
+       git rev-parse --verify v1.0.0-0-g000000000 &&
+
+       # likewise for generation 2 and 4
+       git rev-parse --verify v1.0.0-2-g000000000 &&
+       git rev-parse --verify v1.0.0-4-g000000000
+'
+
+# Note: because rev-parse does not even try to disambiguate based on
+# the generation number, this test currently succeeds for a wrong
+# reason.  When it learns to use the generation number, the previous
+# test should succeed, and also this test should fail because the
+# describe name used in the test with generation number can name two
+# commits.  Make sure that such a future enhancement does not randomly
+# pick one.
+test_expect_success 'parse describe name not ignoring ambiguity' '
+       # ambiguous at the object name level, and there are two such
+       # commits at generation 1
+       test_must_fail git rev-parse --verify v1.0.0-1-g000000000
+'
+
+test_expect_success 'ambiguous commit-ish' '
+       # Now there are many commits that begin with the
+       # common prefix, none of these should pick one at
+       # random.  They all should result in ambiguity errors.
+       test_must_fail git rev-parse --verify 110282^{commit} &&
+
+       # likewise
+       test_must_fail git log 000000000..000000000 &&
+       test_must_fail git log ..000000000 &&
+       test_must_fail git log 000000000.. &&
+       test_must_fail git log 000000000...000000000 &&
+       test_must_fail git log ...000000000 &&
+       test_must_fail git log 000000000...
+'
+
+test_expect_success 'rev-parse --disambiguate' '
+       # The test creates 16 objects that share the prefix and two
+       # commits created by commit-tree in earlier tests share a
+       # different prefix.
+       git rev-parse --disambiguate=000000000 >actual &&
+       test $(wc -l <actual) = 16 &&
+       test "$(sed -e "s/^\(.........\).*/\1/" actual | sort -u)" = 000000000
+'
+
+test_done