revision: do not peel tags used in range notation

A range notation "A..B" means exactly the same thing as what "^A B"
means, i.e. the set of commits that are reachable from B but not
from A.  But the internal representation after the revision parser
parsed these two notations are subtly different.

 - "rev-list ^A B" leaves A and B in the revs->pending.objects[]
   array, with the former marked as UNINTERESTING and the revision
   traversal machinery propagates the mark to underlying commit
   objects A^0 and B^0.

 - "rev-list A..B" peels tags and leaves A^0 (marked as
   UNINTERESTING) and B^0 in revs->pending.objects[] array before
   the traversal machinery kicks in.

This difference usually does not matter, but starts to matter when
the --objects option is used.  For example, we see this:

    $ git rev-list --objects v1.8.4^1..v1.8.4 | grep $(git rev-parse v1.8.4)
    $ git rev-list --objects v1.8.4 ^v1.8.4^1 | grep $(git rev-parse v1.8.4)
    04f013dc38d7512eadb915eba22efc414f18b869 v1.8.4

With the former invocation, the revision traversal machinery never
hears about the tag v1.8.4 (it only sees the result of peeling it,
i.e. the commit v1.8.4^0), and the tag itself does not appear in the
output.  The latter does send the tag object itself to the output.

Make the range notation keep the unpeeled objects and feed them to
the traversal machinery to fix this inconsistency.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 45 insertions, 22 deletions

diff --git a/revision.c b/revision.c
index 68545c8015..7010aff817 100644
--- a/revision.c
+++ b/revision.c
@@ -1157,41 +1157,56 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
 		}
 		if (!get_sha1_committish(this, from_sha1) &&
 		    !get_sha1_committish(next, sha1)) {
-			struct commit *a, *b;
-			struct commit_list *exclude;
-
-			a = lookup_commit_reference(from_sha1);
-			b = lookup_commit_reference(sha1);
-			if (!a || !b) {
-				if (revs->ignore_missing)
-					return 0;
-				die(symmetric ?
-				    "Invalid symmetric difference expression %s...%s" :
-				    "Invalid revision range %s..%s",
-				    arg, next);
-			}
+			struct object *a_obj, *b_obj;
 
 			if (!cant_be_filename) {
 				*dotdot = '.';
 				verify_non_filename(revs->prefix, arg);
 			}
 
-			if (symmetric) {
+			a_obj = parse_object(from_sha1);
+			b_obj = parse_object(sha1);
+			if (!a_obj || !b_obj) {
+			missing:
+				if (revs->ignore_missing)
+					return 0;
+				die(symmetric
+				    ? "Invalid symmetric difference expression %s"
+				    : "Invalid revision range %s", arg);
+			}
+
+			if (!symmetric) {
+				/* just A..B */
+				a_flags = flags_exclude;
+			} else {
+				/* A...B -- find merge bases between the two */
+				struct commit *a, *b;
+				struct commit_list *exclude;
+
+				a = (a_obj->type == OBJ_COMMIT
+				     ? (struct commit *)a_obj
+				     : lookup_commit_reference(a_obj->sha1));
+				b = (b_obj->type == OBJ_COMMIT
+				     ? (struct commit *)b_obj
+				     : lookup_commit_reference(b_obj->sha1));
+				if (!a || !b)
+					goto missing;
 				exclude = get_merge_bases(a, b, 1);
 				add_pending_commit_list(revs, exclude,
 							flags_exclude);
 				free_commit_list(exclude);
+
 				a_flags = flags | SYMMETRIC_LEFT;
-			} else
-				a_flags = flags_exclude;
-			a->object.flags |= a_flags;
-			b->object.flags |= flags;
-			add_rev_cmdline(revs, &a->object, this,
+			}
+
+			a_obj->flags |= a_flags;
+			b_obj->flags |= flags;
+			add_rev_cmdline(revs, a_obj, this,
 					REV_CMD_LEFT, a_flags);
-			add_rev_cmdline(revs, &b->object, next,
+			add_rev_cmdline(revs, b_obj, next,
 					REV_CMD_RIGHT, flags);
-			add_pending_object(revs, &a->object, this);
-			add_pending_object(revs, &b->object, next);
+			add_pending_object(revs, a_obj, this);
+			add_pending_object(revs, b_obj, next);
 			return 0;
 		}
 		*dotdot = '.';
diff --git a/t/t6000-rev-list-misc.sh b/t/t6000-rev-list-misc.sh
index b10685af4e..15e3d6476c 100755
--- a/t/t6000-rev-list-misc.sh
+++ b/t/t6000-rev-list-misc.sh
@@ -48,4 +48,12 @@ test_expect_success 'rev-list --objects with pathspecs and copied files' '
 	! grep one output
 '
 
+test_expect_success 'rev-list A..B and rev-list ^A B are the same' '
+	git commit --allow-empty -m another &&
+	git tag -a -m "annotated" v1.0 &&
+	git rev-list --objects ^v1.0^ v1.0 >expect &&
+	git rev-list --objects v1.0^..v1.0 >actual &&
+	test_cmp expect actual
+'
+
 test_done