Subject: Re: [PATCH] reachable.c: add HEAD to reachability starting commits

From: Jeff King <[email-masked]>
Date: Sun, 31 Aug 2014 11:28:06 -0400

On Sat, Aug 30, 2014 at 11:58:35PM +0300, Max Kirillov wrote:

> HEAD is not explicitly used as a starting commit for
> calculating reachability, so if it's detached and reflogs
> are disabled it may be pruned.

Eek, you're right. I think nobody noticed because the HEAD reflog
usually picks it up (and you do not usually detach HEAD on a bare repo).
But I agree we should include it to cover this case.

> diff --git a/reachable.c b/reachable.c
> index 654a8c5..6f6835b 100644
> --- a/reachable.c
> +++ b/reachable.c
> @@ -229,6 +229,9 @@ void mark_reachable_objects(struct rev_info *revs, int mark_reflog,
>  	/* Add all external refs */
>  	for_each_ref(add_one_ref, revs);
>  
> +	/* detached HEAD is not included in the list above */
> +	head_ref(add_one_ref, revs);
> +
>  	/* Add all reflog info */
>  	if (mark_reflog)
>  		for_each_reflog(add_one_reflog, revs);

Looks obviously correct.

> diff --git a/t/t5312-prune-detached.sh b/t/t5312-prune-detached.sh
> new file mode 100755
> index 0000000..fac93e1
> --- /dev/null
> +++ b/t/t5312-prune-detached.sh
> @@ -0,0 +1,19 @@
> +#!/bin/sh
> +
> +test_description='no prune detached head without reflog'
> +. ./test-lib.sh
> +
> +test_expect_success 'make repo' '
> +	git config core.logAllRefUpdates false
> +	git commit --allow-empty -m commit1 &&
> +	git commit --allow-empty -m commit2 &&
> +	git checkout  --detach master &&
> +	git commit --allow-empty -m commit3
> +'
> +
> +test_expect_success 'prune does not delete anything' '
> +	git prune -n >prune_actual &&
> +	: >prune_expected &&
> +	test_cmp prune_expected prune_actual'
> +
> +test_done

Your test looks reasonable, but is there any reason it cannot go in
t5304 with the other prune tests?

-Peff