sha1_name.c: many short names can only be committish

We know that the token "$name" that appear in "$name^{commit}",
"$name^4", "$name~4" etc. can only name a committish (either a
commit or a tag that peels to a commit).  Teach get_short_sha1() to
take advantage of that knowledge when disambiguating an abbreviated
SHA-1 given as an object name.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 2d91dbd958..1508fdb77a 100644
--- a/cache.h
+++ b/cache.h
@@ -813,6 +813,7 @@ struct object_context {
 
 #define GET_SHA1_QUIETLY 01
 #define GET_SHA1_COMMIT 02
+#define GET_SHA1_COMMITTISH 04
 
 extern int get_sha1(const char *str, unsigned char *sha1);
 extern void maybe_die_on_misspelt_object_name(const char *name, const char *prefix);