Re: [PATCH 6/6] push: honor branch.*.push

[Johan Herland <johan@herland.net>]

On Mon, Jun 24, 2013 at 4:19 PM, Ramkumar Ramachandra
<artagnon@gmail.com> wrote:
> Junio C Hamano wrote:
>>>   # on branch master, derived from origin
>>>   $ git push ram
>>>
>>> And branch.master.push is set to next?  Will you let her shoot herself
>>> in the foot like this?
>>
>> It is not shooting in the foot, if branch.master.push is explicitly
>> set to update next.  I do not see any issue in that part.
>
> The question does not pertain to master being mapped to next; it
> pertains to central-workflow versus triangular-workflow: origin versus
> ram.  If the user has set push.default to upstream, she _expects_
> triangular pushes to always be denied, and this is the first violation
> of that rule.  I'm tilting towards building a dependency between
> branch.<name>.push and push.default.

I haven't followed this topic closely, and the concern described below
is probably a consequence of that. Please ignore if my worries are
unfounded.

It seems to me like we're adding (or have already added) quite a bit
of config variables and command-line options for specifying (at
varying levels of specificity and overridability) either the remote to
push to ($remote), or what ref to push into on the remote
($remote_ref). It worries me that we allow $remote and $remote_ref to
be set _separately_ and at separate levels of specificity. I wonder if
this too easily allows users to shoot themselves in the foot by
specifying $remote in one place (e.g. on the command line), then (in
their mind - unrelated) specifying $remote_ref in another place (e.g.
branch.foo.push), and then being negatively surprised when the two
conspire to push into the "wrong" $remote and/or $remote_ref.

I haven't yet dug deep enough to figure out an obvious failure mode
(and I probably should not have sent this email until I'd found one),
but I wonder if we'd be better off forcing the $remote and $remote_ref
configuration for a given branch to appear as more of a single unit.

What if, when setting up tracking for a given branch, we immediately
specified its complete pull and push targets?

For example, when in a centralized workflow (e.g. push.default =
upstream) and we're checking out local branch foo from origin's foo,
we could set up the following configuration [1]:

[branch "foo"]
    pull = origin/foo
    push = origin/foo

In a triangular workflow (assuming we had configuration to specify
such, and also a default push remote), we could then instead set up
the following config:

[branch "foo"]
    pull = origin/foo
    push = my_public/foo

This leaves no ambiguity for even the most novice user as to the pull
and push targets for a given branch, and it's also easy to change it,
either by editing the config file directly, or by using hypothetical
commands:

  git branch foo --pulls-from=origin/bar
  git branch foo --pushes-to=other_repo/foo

Any "git pull" without arguments will fail if branch.<current>.pull is
unset or invalid. Likewise any "git push" without arguments will fail
if branch.<current>.push is unset or invalid.

Obviously, specifying the remote and/or refspec on the command-line
would still override, as it does today, but for the argument-less
forms of "git pull" and "git push", the hierarchy of options and
defaults being consulted to figure out $remote and $remote_ref would
be small and easily understandable.


...Johan


[1]: I do realize that I'm abusing the "foo/bar" notation to mean
"$remote/$ref", and that this does not work in the general case where
both remote names and ref names may contain slashes, or when remote
names don't correspond to eponymous ref namespaces...

-- 
Johan Herland, <johan@herland.net>
www.herland.net