checkout: don't check worktrees when not necessary

When --patch or pathspecs are passed to git checkout, the working tree
will not be switching branch, so there's no need to check if the branch
that we are running checkout on is already checked out.

Original-patch-by: Spencer Baugh <sbaugh@catern.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/checkout.c

@@ -1085,7 +1085,6 @@ static int parse_branchname_arg(int argc, const char **argv,
 {
 	struct tree **source_tree = &opts->source_tree;
 	const char **new_branch = &opts->new_branch;
-	int force_detach = opts->force_detach;
 	int argcount = 0;
 	unsigned char branch_rev[20];
 	const char *arg;
@@ -1206,17 +1205,6 @@ static int parse_branchname_arg(int argc, const char **argv,
 	else
 		new->path = NULL; /* not an existing branch */
 
-	if (new->path && !force_detach && !*new_branch) {
-		unsigned char sha1[20];
-		int flag;
-		char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
-		if (head_ref &&
-		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
-		    !opts->ignore_other_worktrees)
-			check_linked_checkouts(new);
-		free(head_ref);
-	}
-
 	new->commit = lookup_commit_reference_gently(rev, 1);
 	if (!new->commit) {
 		/* not a commit */
@@ -1296,6 +1284,17 @@ static int checkout_branch(struct checkout_opts *opts,
 		die(_("Cannot switch branch to a non-commit '%s'"),
 		    new->name);
 
+	if (new->path && !opts->force_detach && !opts->new_branch) {
+		unsigned char sha1[20];
+		int flag;
+		char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
+		if (head_ref &&
+		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
+		    !opts->ignore_other_worktrees)
+			check_linked_checkouts(new);
+		free(head_ref);
+	}
+
 	if (opts->new_worktree)
 		return prepare_linked_checkout(opts, new);
 

t/t2025-checkout-to.sh

@@ -28,6 +28,14 @@ test_expect_success 'checkout --to refuses to checkout locked branch' '
 	! test -d .git/worktrees/zere
 '
 
+test_expect_success 'checking out paths not complaining about linked checkouts' '
+	(
+	cd existing_empty &&
+	echo dirty >>init.t &&
+	git checkout master -- init.t
+	)
+'
+
 test_expect_success 'checkout --to a new worktree' '
 	git rev-parse HEAD >expect &&
 	git checkout --detach --to here master &&