Subject: Re: [PATCH v2 2/3] refs: add option core.logAllRefUpdates = always

From: Junio C Hamano <[email-masked]>
Date: Thu, 26 Jan 2017 15:39:37 -0800

[email-masked] writes:

> From: Cornelius Weig <[email-masked]>
>
> When core.logallrefupdates is true, we only create a new reflog for refs
> that are under certain well-known hierarchies. The reason is that we
> know that some hierarchies (like refs/tags) do not typically change, and

s/do not typically/are not meant to/;

> that unknown hierarchies might not want reflogs at all (e.g., a
> hypothetical refs/foo might be meant to change often and drop old
> history immediately).
>
> However, sometimes it is useful to override this decision and simply log
> for all refs, because the safety and audit trail is more important than
> the performance implications of keeping the log around.
>
> This patch introduces a new "always" mode for the core.logallrefupdates
> option which will log updates to everything under refs/, regardless
> where in the hierarchy it is (we still will not log things like
> ORIG_HEAD and FETCH_HEAD, which are known to be transient).

OK.

> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 3cd8030..2117616 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -522,6 +522,8 @@ core.logAllRefUpdates::
>  	refs/heads/), remote refs (i.e. under refs/remotes/),
>  	`refs/heads/`), remote refs (i.e. under `refs/remotes/`),

Ahh, the answer to my question on 1/3 is "no, the commit that the
patch was taken out of was already wrong, still having the old line
in front of its rewrite".

>  	note refs (i.e. under `refs/notes/`), and the symbolic ref `HEAD`.
> +	If it is set to `always`, then a missing reflog is automatically
> +	created for any ref under `refs/`.
>  +

OK.

> diff --git a/Documentation/git-tag.txt b/Documentation/git-tag.txt
> index 5055a96..2ac25a9 100644
> --- a/Documentation/git-tag.txt
> +++ b/Documentation/git-tag.txt
> @@ -150,7 +150,8 @@ This option is only applicable when listing tags without annotation lines.
>  	'strip' removes both whitespace and commentary.
>  
>  --create-reflog::
> -	Create a reflog for the tag.
> +	Create a reflog for the tag. To globally enable reflogs for tags, see
> +	`core.logAllRefUpdates` in linkgit:git-config[1].

OK.

> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index bfe685c..1db0b44 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -612,7 +612,7 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
>  	const char *old_desc, *reflog_msg;
>  	if (opts->new_branch) {
>  		if (opts->new_orphan_branch) {
> -			if (opts->new_branch_log && !log_all_ref_updates) {
> +			if (opts->new_branch_log && should_autocreate_reflog("refs/heads/")) {

This is inviting a maintenance nightmare.  The helper function is
defined to take the final refname, not a leading directory name.
That is why you named the parameter "refname" in your patch like
this:

    --- a/refs.h
    +++ b/refs.h
    @@ -64,6 +64,8 @@ int read_ref(const char *refname, unsigned char *sha1);

     int ref_exists(const char *refname);

    +int should_autocreate_reflog(const char *refname);
    +
     int is_branch(const char *refname);

The callers are not supposed to know that its current implementation
happens to only use the leading prefix.  When the definition of this
helper function is changed (e.g. imagine a future where this
"log.allrefupdate" is further enhanced to take glob patterns to
match the refname against), this may break and nobody would notice
for a few weeks, and we will get a regression report after a release
is made.

Don't we have the refname for the branch already in this codepath?

> diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
> index d4fb977..b9084ca 100755
> --- a/t/t1400-update-ref.sh
> +++ b/t/t1400-update-ref.sh
> @@ -93,6 +93,42 @@ test_expect_success 'update-ref creates reflogs with --create-reflog' '
>  	git reflog exists $outside
>  '
>  
> +test_expect_success 'core.logAllRefUpdates=true does not create reflog by default' '
> +	test_config core.logAllRefUpdates true &&
> +	test_when_finished "git update-ref -d $outside" &&
> +	git update-ref $outside $A &&
> +	git rev-parse $A >expect &&
> +	git rev-parse $outside >actual &&
> +	test_cmp expect actual &&
> +	test_must_fail git reflog exists $outside
> +'
> +
> +test_expect_success 'core.logAllRefUpdates=always creates reflog by default' '
> +	test_config core.logAllRefUpdates always &&
> +	test_when_finished "git update-ref -d $outside" &&
> +	git update-ref $outside $A &&
> +	git rev-parse $A >expect &&
> +	git rev-parse $outside >actual &&
> +	test_cmp expect actual &&
> +	git reflog exists $outside
> +'

You might want to add two tests for your original motivation, i.e.

	test_config core.logAllRefUpdates always &&
	git tag a-tag &&
	git reflog exists refs/tags/a-tag

and the other one that does not give reflog for a tag.

Other than that, looks good to me.