Merge branch 'br/sha1-name-40-hex-no-disambiguation'

When parsing a 40-hex string into the object name, the string is
checked to see if it can be interpreted as a ref so that a warning
can be given for ambiguity. The code kicked in even when the
core.warnambiguousrefs is set to false to squelch this warning, in
which case the cycles spent to look at the ref namespace were an
expensive no-op, as the result was discarded without being used.

* br/sha1-name-40-hex-no-disambiguation:
  sha1_name: don't resolve refs when core.warnambiguousrefs is false

Author: gitster

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));