Subject: Re: check-ref-format: include refs/ in the argument or to strip it?

From: Jonathan Nieder <[email-masked]>
Date: Mon, 25 Aug 2014 11:26:36 -0700

Ronnie Sahlberg wrote:
> On Fri, Aug 22, 2014 at 10:46 PM, Jeff King <[email-masked]> wrote:

>> Yeah, this weird "do not allow refs/foo" behavior has continually
>> confused me. Coincidentally I just noticed a case today where
>> "pack-refs" treats "refs/foo" specially for no good reason:
>>
>>   http://thread.gmane.org/gmane.comp.version-control.git/255729
>>
>> After much head scratching over the years, I am of the opinion that
>> nobody every really _meant_ to prevent "refs/foo", and that code
>> comments like the one you quote above were an attempt to document
>> existing buggy behavior that was really trying to differentiate "HEAD"
>> from "refs/*". That's just my opinion, though. :)

It's still very puzzling to me.  The comment came at the same time as
the behavior, in v0.99.9~120 (git-check-ref-format: reject funny ref
names, 2005-10-13).  Before that, the behavior was even stranger ---
it checked that there was exactly one slash in the argument.

I'm willing to believe we might not want that check any more, though.

[...]
> There are also a lot of places where we assume that a refs will start
> with "refs/heads/" and not just "refs/"
> for_each_branch_ref(), log_ref_setup() (so no reflogs) is_branch() to
> name a few.

for_each_branch_ref is for iterating over local branches, which are
defined as refs that start with refs/heads/*.  Likewise, the only
point of is_branch is to check whether a ref is under refs/heads/*.
That's not an assumption about all refs.

log_ref_setup implements the policy that there are only reflogs for:

 * refs where the reflog was explicitly created ("git branch
   --create-reflog" does this, but for some reason there's no
   corresponding "git update-ref --create-reflog" so people have
   to use mkdir directly for other refs), plus

 * if the '[core] logallrefupdates' configuration is enabled (and it
   is by default for non-bare repositories), then HEAD, refs/heads/*,
   refs/notes/*, and refs/remotes/*.

This is documented in git-config(1) --- see core.logAllRefUpdates.

That way, when tools internally use other refs (e.g., FETCH_HEAD),
git doesn't have to automatically incur the cost of maintaining the
reflog for those.  What other refs should there be reflogs for?  I
haven't thought carefully about this.

It definitely isn't an assumption that *all* refs will match that
pattern.  But it might be worth changing for other reasons.

Jonathan