Re: [PATCH v6 06/10] fast-export: add new --refspec option

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 12, 2013, 23:54 UTC
Message-ID: <xmqqob5pfa6j.fsf@gitster.dls.corp.google.com>
In-Reply-To: <xmqq38n1guo8.fsf@gitster.dls.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 16 quoted lines

> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>> Does it?
>>
>>  % git config remote.origin.fetch '+refs/heads/*:refs/remotes-test/origin/*'
>>  % git fetch origin master
>>  From /home/felipec/dev/git
>>   * branch            master     -> FETCH_HEAD
>>   * [new branch]      master     -> refs/remotes-test/origin/master
>>
>> In this case remote.origin.fetch is determining how to translate ref names, not
>> what gets transferred, *exactly* the same as we are doing with --refspec. And
>> as far as I know, remote.origin.fetch is a refspec.
>
> If you had 'next' and 'pu' branches at the remote, do they get
> fetched with that command line?

More interestingly, if you have

	[remote "mothership"]
		push = +refs/heads/*:refs/remotes/satellite/*

in your configuration and then said

	$ git push mothership master

then configured remote.mothership.push is not even used (I bring this up because "export" is more closely related to "push" than "fetch").

This (and why 'next' and 'pu' are not fetched in the "fetch" example) is because traditionally, refspecs that are explicitly given on the command line overrides configured ones (in other words, configured ones are used as a fallback default).

This is a bit of tangent, but since the recent discussion on the triangular workflows, I've been wondering if we may want to have a new way to configure things so that we can say "When I push to mothership any one of my local branches, I want it to go to the ref with the same name at the mothership under refs/remotes/satellite/ hierarchy (because I am emulating 'git fetch' that is run on the mothership to get updates from this satellite)", somewhat similar to what you added to "fast-export" via the option in question.

But we cannot achieve that mapping by changing the meaning of the configured refspecs remote.mothership.push without having to worry about breaking existing practices of people. When they say "git push mothership master", they do mean to push refs/heads/master to refs/heads/master, and it will break the expectation in their existing repositories if we change the semantics under them.

A possible way to achieve that mapping "When I push to mothership any one of my local branches,..." could be to introduce a _new_ configuration (so that existing repositories will not suddenly change their behaviour):

	[remote "mothership"]
		pushmap = +refs/heads/*:refs/remotes/satellite/*

And then we can allow this command line

	$ git push mothership master

to be affected by the mapping when expanding the short-hand refspecs given on the command line. Traditionally, anything without colon stood as a short-hand for "push to the same name", e.g. 'master' is for 'refs/heads/master:refs/heads/master' in this example, and 'v1.0' would be for 'refs/tags/v1.0:refs/tags/v1.0'.

But it does not have to stay that way. In order to move things forward in that direction, this new configuration has to be distinguishable from the traditional "refspec", as it embodies a different concept.