Merge branch 'nd/worktree-kill-parse-ref' into maint

"git branch -M a b" while on a branch that is completely unrelated
to either branch a or branch b misbehaved when multiple worktree
was in use.  This has been fixed.

* nd/worktree-kill-parse-ref:
  branch: fix branch renaming not updating HEADs correctly

Author: gitster

branch.c

@@ -357,8 +357,9 @@ int replace_each_worktree_head_symref(const char *oldref, const char *newref,
 
 		if (worktrees[i]->is_detached)
 			continue;
-		if (worktrees[i]->head_ref &&
-		    strcmp(oldref, worktrees[i]->head_ref))
+		if (!worktrees[i]->head_ref)
+			continue;
+		if (strcmp(oldref, worktrees[i]->head_ref))
 			continue;
 
 		refs = get_worktree_ref_store(worktrees[i]);

t/t3200-branch.sh

@@ -162,6 +162,19 @@ test_expect_success 'git branch -M baz bam should add entries to .git/logs/HEAD'
 	grep "^0\{40\}.*$msg$" .git/logs/HEAD
 '
 
+test_expect_success 'git branch -M should leave orphaned HEAD alone' '
+	git init orphan &&
+	(
+		cd orphan &&
+		test_commit initial &&
+		git checkout --orphan lonely &&
+		grep lonely .git/HEAD &&
+		test_path_is_missing .git/refs/head/lonely &&
+		git branch -M master mistress &&
+		grep lonely .git/HEAD
+	)
+'
+
 test_expect_success 'resulting reflog can be shown by log -g' '
 	oid=$(git rev-parse HEAD) &&
 	cat >expect <<-EOF &&

worktree.c

@@ -30,7 +30,7 @@ static void add_head_info(struct worktree *wt)
 
 	target = refs_resolve_ref_unsafe(get_worktree_ref_store(wt),
 					 "HEAD",
-					 RESOLVE_REF_READING,
+					 0,
 					 wt->head_sha1, &flags);
 	if (!target)
 		return;