Hi Anders,

responding here instead of to the cover letter (because there is none
;-)): great work!

Others pointed out the really tiny nit that some phrases should start with
lower-case, which would be nice to see addressed. I did not find any major
issue anymore (apart from the slightly iffy assumption that `buf->ref`
starts with `refs/heads/` and therefore `buf->ref + strlen("refs/heads/")`
would not overrun, but I _think_ the current code enforces that prefix
somewhere along the lines), so:

	Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Thank you for this contribution!
Dscho

On Tue, 9 Nov 2021, Anders Kaseorg wrote:

> 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
>
> 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 <andersk@mit.edu>
> ---
>  builtin/fetch.c       | 29 +++++++++++++++--------------
>  t/t5516-fetch-push.sh | 18 ++++++++++++++++++
>  2 files changed, 33 insertions(+), 14 deletions(-)
>
> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index f7abbc31ff..ed8a906717 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 +855,7 @@ static int update_local_ref(struct ref *ref,
>  			    int summary_width)
>  {
>  	struct commit *current = NULL, *updated;
> -	struct branch *current_branch = branch_get(NULL);
> +	const struct worktree *wt;
>  	const char *pretty_ref = prettify_refname(ref->name);
>  	int fast_forward = 0;
>
> @@ -868,16 +869,18 @@ 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 &&
> +	    (wt = find_shared_symref("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;
>  	}
> @@ -1387,16 +1390,14 @@ 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)) &&
> +		    !wt->is_bare)
> +			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..f07e32126f 100755
> --- a/t/t5516-fetch-push.sh
> +++ b/t/t5516-fetch-push.sh
> @@ -1771,4 +1771,22 @@ 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
> --
> 2.33.1
>
>