Subject: Re: [PATCH v2 4/4] gc: remove broken symrefs

From: Junio C Hamano <[email-masked]>
Date: Mon, 28 Sep 2015 11:41:25 -0700

Johannes Schindelin <[email-masked]> writes:

> When encountering broken symrefs, such as a stale remote HEAD (which can
> happen if the active branch was renamed in the remote), it is more
> helpful to remove those symrefs than to exit with an error.

I think this depends on the perspective.  One side of me says that a
remote HEAD that points at refs/remotes/origin/topic that no longer
exists is still giving me a valuable information and it should take
a conscious action by the user to remove it, or evne better to
repoint it to a more useful place.  And from that point of view,
removing is not all that helpful.  Keeping them and not allowing
them to exit with an error would be a real improvement.

On the other hand, I can certainly understand a view that considers
that such a dangling symbolic ref is merely a cruft like any other
cruft, and "gc" is all about removing cruft.

It just feels to me that this is a bit more valuable than other
kinds of cruft, but maybe it is just me.

>
> This fixes https://github.com/git-for-windows/git/issues/423
>
> Signed-off-by: Johannes Schindelin <[email-masked]>
> ---
>  builtin/prune.c | 12 +++++++++++-
>  t/t6500-gc.sh   |  2 +-
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/prune.c b/builtin/prune.c
> index d6f664f..337b12a 100644
> --- a/builtin/prune.c
> +++ b/builtin/prune.c
> @@ -6,6 +6,7 @@
>  #include "reachable.h"
>  #include "parse-options.h"
>  #include "progress.h"
> +#include "refs.h"
>  
>  static const char * const prune_usage[] = {
>  	N_("git prune [-n] [-v] [--expire <time>] [--] [<head>...]"),
> @@ -100,6 +101,7 @@ static void remove_temporary_files(const char *path)
>  int cmd_prune(int argc, const char **argv, const char *prefix)
>  {
>  	struct rev_info revs;
> +	struct string_list broken_symrefs = STRING_LIST_INIT_DUP;
>  	struct progress *progress = NULL;
>  	const struct option options[] = {
>  		OPT__DRY_RUN(&show_only, N_("do not remove, show only")),
> @@ -110,6 +112,7 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>  		OPT_END()
>  	};
>  	char *s;
> +	int i;
>  
>  	expire = ULONG_MAX;
>  	save_commit_buffer = 0;
> @@ -136,7 +139,14 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>  	if (show_progress)
>  		progress = start_progress_delay(_("Checking connectivity"), 0, 0, 2);
>  
> -	mark_reachable_objects(&revs, 1, expire, progress, NULL);
> +	revs.ignore_missing = 1;
> +	mark_reachable_objects(&revs, 1, expire, progress, &broken_symrefs);
> +	for (i = 0; i < broken_symrefs.nr; i++) {
> +		char *path = broken_symrefs.items[i].string;
> +		printf("Removing stale ref %s\n", path);
> +		if (!show_only && delete_ref(path, NULL, REF_NODEREF))
> +			die("Could not remove stale ref %s", path);
> +	}
>  	stop_progress(&progress);
>  	for_each_loose_file_in_objdir(get_object_directory(), prune_object,
>  				      prune_cruft, prune_subdir, NULL);
> diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
> index b736774..0ae4271 100755
> --- a/t/t6500-gc.sh
> +++ b/t/t6500-gc.sh
> @@ -30,7 +30,7 @@ test_expect_success 'gc -h with invalid configuration' '
>  	test_i18ngrep "[Uu]sage" broken/usage
>  '
>  
> -test_expect_failure 'gc removes broken refs/remotes/<name>/HEAD' '
> +test_expect_success 'gc removes broken refs/remotes/<name>/HEAD' '
>  	git init remote &&
>  	(
>  		cd remote &&