Re: [PATCH v6 5/8] fetch: protect branches checked out in all worktrees

As a side effect of using find_shared_symref, we’ll also refuse the
fetch when we’re on a detached HEAD because we’re rebasing or bisecting
on the branch in question. This seems like a sensible change.

Signed-off-by: Anders Kaseorg <redacted>
---
 builtin/fetch.c       | 75 +++++++++++++++++++++++--------------------
 t/t5516-fetch-push.sh | 18 +++++++++++
 2 files changed, 58 insertions(+), 35 deletions(-)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index e5971fa6e5..f373252490 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)

@@ -840,14 +841,13 @@ static void format_display(struct strbuf *display, char code,

 static int update_local_ref(struct ref *ref,
 			    struct ref_transaction *transaction,
-			    const char *remote,
-			    const struct ref *remote_ref,
-			    struct strbuf *display,
-			    int summary_width)
+			    const char *remote, const struct ref *remote_ref,
+			    struct strbuf *display, int summary_width,

+			    struct worktree **worktrees)
 {
 	struct commit *current = NULL, *updated;
 	enum object_type type;
-	struct branch *current_branch = branch_get(NULL);
+	const struct worktree *wt;
 	const char *pretty_ref = prettify_refname(ref->name);
 	int fast_forward = 0;

@@ -862,16 +862,17 @@ 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()) &&
-	    !is_null_oid(&ref->old_oid)) {
+	if (!update_head_ok &&
+	    (wt = find_shared_symref(worktrees, "HEAD", ref->name)) &&
+	    !wt->is_bare && !is_null_oid(&ref->old_oid)) {
 		/*
 		 * If this is the head, and it's not okay to update
 		 * the head, and the old value of the head isn't empty...
 		 */
 		format_display(display, '!', _("[rejected]"),
-			       _("can't fetch in current branch"),
+			       wt->is_current ?
+				       _("can't fetch in current branch") :
+				       _("checked out in another worktree"),
 			       remote, pretty_ref, summary_width);
 		return 1;
 	}

@@ -1071,7 +1072,8 @@ N_("it took %.2f seconds to check forced updates; you can use\n"
    " to avoid this check\n");

 static int store_updated_refs(const char *raw_url, const char *remote_name,
-			      int connectivity_checked, struct ref *ref_map)
+			      int connectivity_checked, struct ref *ref_map,
+			      struct worktree **worktrees)
 {
 	struct fetch_head fetch_head;
 	struct commit *commit;

@@ -1188,7 +1190,8 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 			strbuf_reset(&note);
 			if (ref) {
 				rc |= update_local_ref(ref, transaction, what,
-						       rm, &note, summary_width);
+						       rm, &note, summary_width,
+						       worktrees);
 				free(ref);
 			} else if (write_fetch_head || dry_run) {
 				/*

@@ -1301,16 +1304,15 @@ static int fetch_refs(struct transport *transport, struct ref *ref_map)
 }

 /* Update local refs based on the ref values fetched from a remote */
-static int consume_refs(struct transport *transport, struct ref *ref_map)
+static int consume_refs(struct transport *transport, struct ref *ref_map,
+			struct worktree **worktrees)
 {
 	int connectivity_checked = transport->smart_options
 		? transport->smart_options->connectivity_checked : 0;
 	int ret;
 	trace2_region_enter("fetch", "consume_refs", the_repository);
-	ret = store_updated_refs(transport->url,
-				 transport->remote->name,
-				 connectivity_checked,
-				 ref_map);
+	ret = store_updated_refs(transport->url, transport->remote->name,
+				 connectivity_checked, ref_map, worktrees);

 	transport_unlock_pack(transport);
 	trace2_region_leave("fetch", "consume_refs", the_repository);
 	return ret;

@@ -1643,7 +1647,7 @@ static int do_fetch(struct transport *transport,
 				  "you need to specify exactly one branch with the --set-upstream option"));
 		}
 	}
- skip:
+skip:

@@ -1653,11 +1657,12 @@ static int do_fetch(struct transport *transport,
 		ref_map = NULL;
 		find_non_local_tags(remote_refs, &ref_map, &tail);
 		if (ref_map)
-			backfill_tags(transport, ref_map);
+			backfill_tags(transport, ref_map, worktrees);
 		free_refs(ref_map);
 	}

- cleanup:
+cleanup:

+	free_worktrees(worktrees);
 	return retcode;
 }

diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 4db8edd9c8..36fb90f4b0 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh

@@ -1770,4 +1770,22 @@ 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_when_finished "git worktree remove --force wt && git branch -D wt" &&
+	git worktree add wt &&
+	test_commit apple &&
+	test_must_fail git fetch . HEAD:wt &&
+	git fetch -u . HEAD:wt
+'
+
+test_expect_success 'refuse fetch to current branch of bare repository worktree' '
+	test_when_finished "rm -fr bare.git" &&
+	git clone --bare . bare.git &&
+	git -C bare.git worktree add wt &&
+	test_commit banana &&
+	test_must_fail git -C bare.git fetch .. HEAD:wt &&
+	git -C bare.git fetch -u .. HEAD:wt
+'
+
 test_done