worktree add: stop reading ".git/HEAD"

The function can_use_local_refs() prints a warning if there are no local
branches and HEAD is invalid or points to an unborn branch. As part of
the warning it prints the contents of ".git/HEAD". In a repository using
the reftable backend HEAD is not stored in the filesystem so reading
that file is pointless. In a repository using the files backend it is
unclear how useful printing it is - it would be better to diagnose the
problem for the user. For now, simplify the warning by not printing
the file contents and adjust the relevant test case accordingly. Also
fixup the test case to use test_grep so that anyone trying to debug a
test failure in the future is not met by a wall of silence.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: phillipwood

builtin/worktree.c

@@ -692,25 +692,8 @@ static int can_use_local_refs(const struct add_opts *opts)
 	if (refs_head_ref(get_main_ref_store(the_repository), first_valid_ref, NULL)) {
 		return 1;
 	} else if (refs_for_each_branch_ref(get_main_ref_store(the_repository), first_valid_ref, NULL)) {
-		if (!opts->quiet) {
-			struct strbuf path = STRBUF_INIT;
-			struct strbuf contents = STRBUF_INIT;
-			char *wt_gitdir = get_worktree_git_dir(NULL);
-
-			strbuf_add_real_path(&path, wt_gitdir);
-			strbuf_addstr(&path, "/HEAD");
-			strbuf_read_file(&contents, path.buf, 64);
-			strbuf_stripspace(&contents, NULL);
-			strbuf_strip_suffix(&contents, "\n");
-
-			warning(_("HEAD points to an invalid (or orphaned) reference.\n"
-				  "HEAD path: '%s'\n"
-				  "HEAD contents: '%s'"),
-				  path.buf, contents.buf);
-			strbuf_release(&path);
-			strbuf_release(&contents);
-			free(wt_gitdir);
-		}
+		if (!opts->quiet)
+			warning(_("HEAD points to an invalid (or orphaned) reference.\n"));
 		return 1;
 	}
 	return 0;

t/t2400-worktree-add.sh

@@ -987,7 +987,7 @@ test_dwim_orphan () {
 				then
 					test_must_be_empty actual
 				else
-					grep "$info_text" actual
+					test_grep "$info_text" actual
 				fi
 			elif [ "$outcome" = "no_infer" ]
 			then
@@ -996,39 +996,35 @@ test_dwim_orphan () {
 				then
 					test_must_be_empty actual
 				else
-					! grep "$info_text" actual
+					test_grep ! "$info_text" actual
 				fi
 			elif [ "$outcome" = "fetch_error" ]
 			then
 				test_must_fail git $dashc_args worktree add $args 2>actual &&
-				grep "$fetch_error_text" actual
+				test_grep "$fetch_error_text" actual
 			elif [ "$outcome" = "fatal_orphan_bad_combo" ]
 			then
 				test_must_fail git $dashc_args worktree add $args 2>actual &&
 				if [ $use_quiet -eq 1 ]
 				then
-					! grep "$info_text" actual
+					test_grep ! "$info_text" actual
 				else
-					grep "$info_text" actual
+					test_grep "$info_text" actual
 				fi &&
-				grep "$bad_combo_regex" actual
+				test_grep "$bad_combo_regex" actual
 			elif [ "$outcome" = "warn_bad_head" ]
 			then
 				test_must_fail git $dashc_args worktree add $args 2>actual &&
 				if [ $use_quiet -eq 1 ]
 				then
-					grep "$invalid_ref_regex" actual &&
-					! grep "$orphan_hint" actual
+					test_grep "$invalid_ref_regex" actual &&
+					test_grep ! "$orphan_hint" actual
 				else
-					headpath=$(git $dashc_args rev-parse --path-format=absolute --git-path HEAD) &&
-					headcontents=$(cat "$headpath") &&
-					grep "HEAD points to an invalid (or orphaned) reference" actual &&
-					grep "HEAD path: .$headpath." actual &&
-					grep "HEAD contents: .$headcontents." actual &&
-					grep "$orphan_hint" actual &&
-					! grep "$info_text" actual
+					test_grep "HEAD points to an invalid (or orphaned) reference" actual &&
+					test_grep "$orphan_hint" actual &&
+					test_grep ! "$info_text" actual
 				fi &&
-				grep "$invalid_ref_regex" actual
+				test_grep "$invalid_ref_regex" actual
 			else
 				# Unreachable
 				false