[PATCH] sha1_name: don't resolve refs when core.warnambiguousrefs is false

[Brodie Rao <brodie@sf.io>]

This change ensures get_sha1_basic() doesn't try to resolve full hashes
as refs when ambiguous ref warnings are disabled.

This provides a substantial performance improvement when passing many
hashes to a command (like "git rev-list --stdin") when
core.warnambiguousrefs is false. The check incurs 6 stat()s for every
hash supplied, which can be costly over NFS.

Signed-off-by: Brodie Rao <brodie@sf.io>
---
 sha1_name.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index e9c2999..10bd007 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -451,9 +451,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	int at, reflog_len, nth_prior = 0;
 
 	if (len == 40 && !get_sha1_hex(str, sha1)) {
-		if (warn_on_object_refname_ambiguity) {
+		if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 			refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
-			if (refs_found > 0 && warn_ambiguous_refs) {
+			if (refs_found > 0) {
 				warning(warn_msg, len, str);
 				if (advice_object_name_warning)
 					fprintf(stderr, "%s\n", _(object_name_msg));
-- 
1.8.5.2