blame: dwim "blame --reverse OLD" as "blame --reverse OLD.."

diff --git a/builtin/blame.c b/builtin/blame.c
index a027b8a6075dd2e300b307c4c20f41a4fbfc9566..574b47dd55b97577b701f61a0aab09e8185e665a 100644 (file)
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2447,6 +2447,41 @@ static char *prepare_final(struct scoreboard *sb)
        return xstrdup_or_null(name);
 }
 
+static const char *dwim_reverse_initial(struct scoreboard *sb)
+{
+       /*
+        * DWIM "git blame --reverse ONE -- PATH" as
+        * "git blame --reverse ONE..HEAD -- PATH" but only do so
+        * when it makes sense.
+        */
+       struct object *obj;
+       struct commit *head_commit;
+       unsigned char head_sha1[20];
+
+       if (sb->revs->pending.nr != 1)
+               return NULL;
+
+       /* Is that sole rev a committish? */
+       obj = sb->revs->pending.objects[0].item;
+       obj = deref_tag(obj, NULL, 0);
+       if (obj->type != OBJ_COMMIT)
+               return NULL;
+
+       /* Do we have HEAD? */
+       if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_sha1, NULL))
+               return NULL;
+       head_commit = lookup_commit_reference_gently(head_sha1, 1);
+       if (!head_commit)
+               return NULL;
+
+       /* Turn "ONE" into "ONE..HEAD" then */
+       obj->flags |= UNINTERESTING;
+       add_pending_object(sb->revs, &head_commit->object, "HEAD");
+
+       sb->final = (struct commit *)obj;
+       return sb->revs->pending.objects[0].name;
+}
+
 static char *prepare_initial(struct scoreboard *sb)
 {
        int i;
@@ -2472,6 +2507,9 @@ static char *prepare_initial(struct scoreboard *sb)
                sb->final = (struct commit *) obj;
                final_commit_name = revs->pending.objects[i].name;
        }
+
+       if (!final_commit_name)
+               final_commit_name = dwim_reverse_initial(sb);
        if (!final_commit_name)
                die("No commit to dig up from?");
        return xstrdup(final_commit_name);