Merge branch 'nd/warn-ambiguous-object-name'

"git cmd <name>", when <name> happens to be a 40-hex string,
directly uses the 40-hex string as an object name, even if a ref
"refs/<some hierarchy>/<name>" exists.  This disambiguation order
is unlikely to change, but we should warn about the ambiguity just
like we warn when more than one refs/ hierachies share the same
name.

* nd/warn-ambiguous-object-name:
  get_sha1: warn about full or short object names that look like refs

1 files changed, 23 insertions, 2 deletions

diff --git a/sha1_name.c b/sha1_name.c
index b3a90e6f05..a695d16d8c 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -435,12 +435,31 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 {
 	static const char *warn_msg = "refname '%.*s' is ambiguous.";
+	static const char *object_name_msg = N_(
+	"Git normally never creates a ref that ends with 40 hex characters\n"
+	"because it will be ignored when you just specify 40-hex. These refs\n"
+	"may be created by mistake. For example,\n"
+	"\n"
+	"  git checkout -b $br $(git rev-parse ...)\n"
+	"\n"
+	"where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
+	"examine these refs and maybe delete them. Turn this message off by\n"
+	"running \"git config advice.object_name_warning false\"");
+	unsigned char tmp_sha1[20];
 	char *real_ref = NULL;
 	int refs_found = 0;
 	int at, reflog_len;
 
-	if (len == 40 && !get_sha1_hex(str, sha1))
+	if (len == 40 && !get_sha1_hex(str, sha1)) {
+		refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
+		if (refs_found > 0 && warn_ambiguous_refs) {
+			warning(warn_msg, len, str);
+			if (advice_object_name_warning)
+				fprintf(stderr, "%s\n", _(object_name_msg));
+		}
+		free(real_ref);
 		return 0;
+	}
 
 	/* basic@{time or number or -number} format to query ref-log */
 	reflog_len = at = 0;
@@ -481,7 +500,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	if (!refs_found)
 		return -1;
 
-	if (warn_ambiguous_refs && refs_found > 1)
+	if (warn_ambiguous_refs &&
+	    (refs_found > 1 ||
+	     !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
 		warning(warn_msg, len, str);
 
 	if (reflog_len) {