[PATCH] diff A...B: do not limit the syntax too narrowly

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 16, 2010, 19:14 UTC
Message-ID: <7vsk3js0gi.fsf@alter.siamese.dyndns.org>

Earlier we tried to make sure that the trees we get are what A...B syntax produced, by checking that earlier ones are all marked uninteresting (which has to be true as they are merge bases), there are two remaining ones that are interesting, and they are marked as non-symmetric-left and symmetric-left respectively.

The "the last two must be interesting" condition is however wrong when one is an ancestor of the other between A and B (i.e. fast-forward). In such a case, one of them is marked uninteresting.

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

 * This breakage should have been obvious (e.g. "git diff master...next"
   should exhibit it).  Sorry about it.

   Also "the second from the last one should not be SYMMETRIC_LEFT"
   condition does not hold if somebody does "git diff HEAD...HEAD", but
   that is a bit of borderline insanity.

   We *could* tighten the rule to say "the last two must be interesting or
   listed as one of the merge bases" to tighten the rule again, but I
   don't think it is worth it.

 builtin-diff.c |   13 -------------
 1 files changed, 0 insertions(+), 13 deletions(-)

diff --git a/builtin-diff.c b/builtin-diff.c
index 62b483b..192cbb2 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -407,19 +407,6 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 		result = builtin_diff_tree(&rev, argc, argv, ent);
 	else if (ent[0].item->flags & UNINTERESTING) {
 		/*
-		 * Perhaps the user gave us A...B, which expands
-		 * to a list of negative merge bases followed by
-		 * A (symmetric-left) and B?  Let's make sure...
-		 */
-		for (i = 1; i < ents; i++)
-			if (!(ent[i].item->flags & UNINTERESTING))
-				break;
-		if (ents != i + 2 ||
-		    (ent[i+1].item->flags & UNINTERESTING) ||
-		    (!(ent[i].item->flags & SYMMETRIC_LEFT)) ||
-		    (ent[i+1].item->flags & SYMMETRIC_LEFT))
-			die("what do you mean by that?");
-		/*
 		 * diff A...B where there is at least one merge base
 		 * between A and B.  We have ent[0] == merge-base,
 		 * ent[ents-2] == A, and ent[ents-1] == B.  Show diff

-- 
1.7.2.rc3.255.g7a7d8