[PATCH FIX-default] pushrace: avoid crash on bare push when using concurrent push mode

[Yuya Nishihara]

On Wed, 28 Jun 2017 18:21:41 +0200, Pierre-Yves David wrote:
> # HG changeset patch
> # User Pierre-Yves David <pierre-yves.david at octobus.net>
> # Date 1498664485 -7200
> #      Wed Jun 28 17:41:25 2017 +0200
> # Node ID c6954352fa654efd0627e2024100f7bc59f5028f
> # Parent  6fdc1518983ed9ed94f83f803bb787adaf92c11b
> # EXP-Topic pushrace
> # Available At https://www.mercurial-scm.org/repo/users/marmoute/mercurial/
> #              hg pull https://www.mercurial-scm.org/repo/users/marmoute/mercurial/ -r c6954352fa65
> pushrace: avoid crash on bare push when using concurrent push mode
> 
> If the remote is empty, we do now bother computing head changes and the
> 'pushbranchmap' attribute stays at None.
> 
> We now handle and tests this case.
> 
> diff --git a/mercurial/exchange.py b/mercurial/exchange.py
> --- a/mercurial/exchange.py
> +++ b/mercurial/exchange.py
> @@ -730,9 +730,10 @@ def _pushb2ctxcheckheads(pushop, bundler
>      # * if we don't push anything, there are nothing to check.
>      if not pushop.force and pushop.outgoing.missingheads:
>          allowunrelated = 'related' in bundler.capabilities.get('checkheads', ())
> -        if not allowunrelated:
> +        emptyremote = pushop.pushbranchmap is None
> +        if not allowunrelated or emptyremote:
>              bundler.newpart('check:heads', data=iter(pushop.remoteheads))
> -        else:
> +        elif pushop.pushbranchmap is not None:

Perhaps this can be just "else:" ?