[PATCH v2] fetch: Protect branches checked out in all worktrees

[Anders Kaseorg <andersk@mit.edu>]

Refuse to fetch into the currently checked out branch of any working
tree, not just the current one.

Fixes this previously reported bug:

https://public-inbox.org/git/cb957174-5e9a-5603-ea9e-ac9b58a2eaad@mathema.de

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
---

(Eep! Sorry for the newline corruption in the previous message. 
Thunderbird has forsaken me.)

 builtin/fetch.c       | 22 +++++++++-------------
 t/t5516-fetch-push.sh | 10 ++++++++++
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index f7abbc31ff..a6549c2ab6 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -28,6 +28,7 @@
 #include "promisor-remote.h"
 #include "commit-graph.h"
 #include "shallow.h"
+#include "worktree.h"
 
 #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
 
@@ -854,7 +855,6 @@ static int update_local_ref(struct ref *ref,
 			    int summary_width)
 {
 	struct commit *current = NULL, *updated;
-	struct branch *current_branch = branch_get(NULL);
 	const char *pretty_ref = prettify_refname(ref->name);
 	int fast_forward = 0;
 
@@ -868,9 +868,8 @@ static int update_local_ref(struct ref *ref,
 		return 0;
 	}
 
-	if (current_branch &&
-	    !strcmp(ref->name, current_branch->name) &&
-	    !(update_head_ok || is_bare_repository()) &&
+	if (!update_head_ok &&
+	    find_shared_symref("HEAD", ref->name) &&
 	    !is_null_oid(&ref->old_oid)) {
 		/*
 		 * If this is the head, and it's not okay to update
@@ -1387,16 +1386,13 @@ static int prune_refs(struct refspec *rs, struct ref *ref_map,
 
 static void check_not_current_branch(struct ref *ref_map)
 {
-	struct branch *current_branch = branch_get(NULL);
-
-	if (is_bare_repository() || !current_branch)
-		return;
-
+	const struct worktree *wt;
 	for (; ref_map; ref_map = ref_map->next)
-		if (ref_map->peer_ref && !strcmp(current_branch->refname,
-					ref_map->peer_ref->name))
-			die(_("Refusing to fetch into current branch %s "
-			    "of non-bare repository"), current_branch->refname);
+		if (ref_map->peer_ref &&
+		    (wt = find_shared_symref("HEAD", ref_map->peer_ref->name)))
+			die(_("Refusing to fetch into branch '%s' "
+			      "checked out at '%s'"),
+			    ref_map->peer_ref->name, wt->path);
 }
 
 static int truncate_fetch_head(void)
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 8212ca56dc..c8cb62c05d 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -1771,4 +1771,14 @@ test_expect_success 'denyCurrentBranch and worktrees' '
 	git -C cloned push origin HEAD:new-wt &&
 	test_must_fail git -C cloned push --delete origin new-wt
 '
+
+test_expect_success 'refuse fetch to current branch of worktree' '
+	test_commit -C cloned second &&
+	test_must_fail git fetch cloned HEAD:new-wt &&
+	git clone --bare . bare.git &&
+	git -C bare.git worktree add bare-wt &&
+	test_must_fail git -C bare.git fetch ../cloned HEAD:bare-wt &&
+	git fetch -u cloned HEAD:new-wt &&
+	git -C bare.git fetch -u ../cloned HEAD:bare-wt
+'
 test_done
-- 
2.33.0