rev-parse: fix meaning of rev~ vs rev~0.

I think it would make more sense for rev~ to have the same guarantees that
rev^ has, namely to always return a commit. I would also suggest that not
giving a number would have the same effect of defaulting to 1, not 0.

Right now it's a bit illogical, but at least it's an _undocumented_
illogical behaviour.

This patch makes '^' and '~' act the same for the default count (i.e. both
default to 1), and also have the same behaviour for a count of zero.

Before (no discernible pattern):

	[torvalds@woody git]$ git rev-parse v1.5.1 v1.5.1^0 v1.5.1~0 v1.5.1^ v1.5.1~
	45354a57ee7e3e42c7137db6c94fa968c6babe8d
	89815cab95268e8f0f58142b848ac4cd5e9cbdcb
	45354a57ee7e3e42c7137db6c94fa968c6babe8d
	045f5759c97746589a067461e50fad16f60711ac
	45354a57ee7e3e42c7137db6c94fa968c6babe8d

After (fairly logical):

	[torvalds@woody git]$ git rev-parse v1.5.1 v1.5.1^0 v1.5.1~0 v1.5.1^ v1.5.1~
	45354a57ee7e3e42c7137db6c94fa968c6babe8d
	89815cab95268e8f0f58142b848ac4cd5e9cbdcb
	89815cab95268e8f0f58142b848ac4cd5e9cbdcb
	045f5759c97746589a067461e50fad16f60711ac
	045f5759c97746589a067461e50fad16f60711ac

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/sha1_name.c b/sha1_name.c
index 13e11645e1fd6b61812cc3e88d2ad6cd42cad9ce..6c9c1c75adefe2d5e38212b75302368293c9137b 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -408,18 +408,22 @@ static int get_nth_ancestor(const char *name, int len,
                            unsigned char *result, int generation)
 {
        unsigned char sha1[20];
-       int ret = get_sha1_1(name, len, sha1);
+       struct commit *commit;
+       int ret;
+
+       ret = get_sha1_1(name, len, sha1);
        if (ret)
                return ret;
+       commit = lookup_commit_reference(sha1);
+       if (!commit)
+               return -1;
 
        while (generation--) {
-               struct commit *commit = lookup_commit_reference(sha1);
-
-               if (!commit || parse_commit(commit) || !commit->parents)
+               if (parse_commit(commit) || !commit->parents)
                        return -1;
-               hashcpy(sha1, commit->parents->item->object.sha1);
+               commit = commit->parents->item;
        }
-       hashcpy(result, sha1);
+       hashcpy(result, commit->object.sha1);
        return 0;
 }
 
@@ -526,9 +530,8 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1)
        int ret, has_suffix;
        const char *cp;
 
-       /* "name~3" is "name^^^",
-        * "name~" and "name~0" are name -- not "name^0"!
-        * "name^" is not "name^0"; it is "name^1".
+       /*
+        * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
         */
        has_suffix = 0;
        for (cp = name + len - 1; name <= cp; cp--) {
@@ -546,11 +549,10 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1)
                cp++;
                while (cp < name + len)
                        num = num * 10 + *cp++ - '0';
-               if (has_suffix == '^') {
-                       if (!num && len1 == len - 1)
-                               num = 1;
+               if (!num && len1 == len - 1)
+                       num = 1;
+               if (has_suffix == '^')
                        return get_parent(name, len1, sha1, num);
-               }
                /* else if (has_suffix == '~') -- goes without saying */
                return get_nth_ancestor(name, len1, sha1, num);
        }