Merge branch 'it/refs-name-conflict'

Expose "name conflict" error when a ref creation fails due to D/F
conflict in the ref namespace, to improve an error message given by
"git fetch".

* it/refs-name-conflict:
  refs: return conflict error when checking packed refs

Author: gitster

refs/files-backend.c

@@ -794,8 +794,10 @@ static int lock_raw_ref(struct files_ref_store *refs,
 		 */
 		if (refs_verify_refname_available(
 				    refs->packed_ref_store, refname,
-				    extras, NULL, err))
+				    extras, NULL, err)) {
+			ret = TRANSACTION_NAME_CONFLICT;
 			goto error_return;
+		}
 	}
 
 	ret = 0;

t/t5510-fetch.sh

@@ -1091,6 +1091,22 @@ test_expect_success 'branchname D/F conflict resolved by --prune' '
 	test_cmp expect actual
 '
 
+test_expect_success 'branchname D/F conflict rejected with targeted error message' '
+	git clone . df-conflict-error &&
+	git branch dir_conflict &&
+	(
+		cd df-conflict-error &&
+		git update-ref refs/remotes/origin/dir_conflict/file HEAD &&
+		test_must_fail git fetch 2>err &&
+		test_grep "error: some local refs could not be updated; try running" err &&
+		test_grep " ${SQ}git remote prune origin${SQ} to remove any old, conflicting branches" err &&
+		git pack-refs --all &&
+		test_must_fail git fetch 2>err-packed &&
+		test_grep "error: some local refs could not be updated; try running" err-packed &&
+		test_grep " ${SQ}git remote prune origin${SQ} to remove any old, conflicting branches" err-packed
+	)
+'
+
 test_expect_success 'fetching a one-level ref works' '
 	test_commit extra &&
 	git reset --hard HEAD^ &&