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List:       git
Subject:    Re: [PATCH 1/1] remote.c: fix handling of push:remote_ref
From:       Jeff King <peff () peff ! net>
Date:       2020-02-28 18:23:49
Message-ID: 20200228182349.GA1408759 () coredump ! intra ! peff ! net
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On Fri, Feb 28, 2020 at 06:24:55PM +0100, Damien Robert wrote:

> To get the meaning of push:remoteref, ref-filter.c calls
> remote_ref_for_branch.
> 
> However remote_ref_for_branch only handles the case of a specified refspec.
> The other cases treated by branch_get_push_1 are the mirror case,
> PUSH_DEFAULT_{NOTHING,MATCHING,CURRENT,UPSTREAM,UNSPECIFIED,SIMPLE}.

Just to back up a minute to the user-visible problem, it's that:

  git config push.default matching
  git for-each-ref --format='%(push)'
  git for-each-ref --format='%(push:remoteref)'

prints a useful tracking ref for the first for-each-ref, but an empty
string for the second. That feature (and remote_ref_for_branch) come
from 9700fae5ee (for-each-ref: let upstream/push report the remote ref
name, 2017-11-07). Author cc'd for guidance.

I wonder if %(upstream:remoteref) has similar problems, but I suppose
not (it doesn't have this implicit config, so we'd always either have a
remote ref or we'd have no upstream at all).

> In all these cases, either there is no push remote, or the remote_ref is
> branch->refname. So we can handle all these cases by returning
> branch->refname, provided that remote is not empty.

In the case of "upstream", the names could be different, couldn't they?

If I do this:

  git init parent
  git -C parent commit --allow-empty -m foo
  
  git clone parent child
  cd child
  git branch --track mybranch origin/master
  git config push.default upstream
  git for-each-ref \
    --format='push=%(push), remoteref=%(push:remoteref)' \
    refs/heads/mybranch

the current code gives no remoteref value, which seems wrong. But with
your patch I'd get "refs/heads/mybranch", which is also wrong.

I think you're right that all of the other cases would always use the
same refname on the remote.

>  remote.c | 5 +++++
>  1 file changed, 5 insertions(+)

We'd want some test coverage to make sure this doesn't regress. There
are already some tests covering this feature in t6300. And indeed, your
patch causes them to fail when checking a "simple" push case (but I
think I'd argue the current expected value there is wrong). That should
be expanded to cover the "upstream" case, too, once we figure out how to
get it right.

> diff --git a/remote.c b/remote.c
> index 593ce297ed..75e42b1e36 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -538,6 +538,11 @@ const char *remote_ref_for_branch(struct branch *branch, int for_push,
>  					*explicit = 1;
>  				return dst;
>  			}
> +			else if (remote) {
> +				if (explicit)
> +					*explicit = 1;
> +				return branch->refname;
> +			}

Saying "*explicit = 1" here seems weird. Isn't the whole point that
these modes _aren't_ explicit?

It looks like our only caller will ignore our return value unless we say
"explicit", though. I have to wonder what the point of that flag is,
versus just returning NULL when we don't have anything to return.

-Peff
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