Merge branch 'mh/reporting-broken-refs-from-for-each-ref' into maint

"git for-each-ref" reported "missing object" for 0{40} when it
encounters a broken ref.  The lack of object whose name is 0{40} is
not the problem; the ref being broken is.

* mh/reporting-broken-refs-from-for-each-ref:
  read_loose_refs(): treat NULL_SHA1 loose references as broken
  read_loose_refs(): simplify function logic
  for-each-ref: report broken references correctly
  t6301: new tests of for-each-ref error handling

1 files changed, 22 insertions, 7 deletions

diff --git a/refs.c b/refs.c
index 67d6745..305bb54 100644
--- a/refs.c
+++ b/refs.c
@@ -1374,19 +1374,34 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
 					 create_dir_entry(refs, refname.buf,
 							  refname.len, 1));
 		} else {
+			int read_ok;
+
 			if (*refs->name) {
 				hashclr(sha1);
 				flag = 0;
-				if (resolve_gitlink_ref(refs->name, refname.buf, sha1) < 0) {
-					hashclr(sha1);
-					flag |= REF_ISBROKEN;
-				}
-			} else if (read_ref_full(refname.buf,
-						 RESOLVE_REF_READING,
-						 sha1, &flag)) {
+				read_ok = !resolve_gitlink_ref(refs->name,
+							       refname.buf, sha1);
+			} else {
+				read_ok = !read_ref_full(refname.buf,
+							 RESOLVE_REF_READING,
+							 sha1, &flag);
+			}
+
+			if (!read_ok) {
 				hashclr(sha1);
 				flag |= REF_ISBROKEN;
+			} else if (is_null_sha1(sha1)) {
+				/*
+				 * It is so astronomically unlikely
+				 * that NULL_SHA1 is the SHA-1 of an
+				 * actual object that we consider its
+				 * appearance in a loose reference
+				 * file to be repo corruption
+				 * (probably due to a software bug).
+				 */
+				flag |= REF_ISBROKEN;
 			}
+
 			if (check_refname_format(refname.buf,
 						 REFNAME_ALLOW_ONELEVEL)) {
 				hashclr(sha1);