push.default and "git push"

push.default and "git push"

[Yuri Kanivetsky]

Hi,

I've been reading the documentation on git push lately, and there are
a couple of places I don't quite understand. From git-config:

> matching - push all branches having the same name on both ends. This makes the repository you are pushing to remember the set of branches that will be pushed out (e.g. if you always push maint and master there and no other branches, the repository you push to will have these two branches, and your local maint and master will be pushed there).

(1) What does "remember" exactly mean? Is this a round-about way to
say that when you push a branch it gets created? But no, it won't push
a branch, unless it exists remotely.

Actually I created a script to examine how these modes work:

https://gist.github.com/x-yuri/20f24f628db1bcbf272c055b33c18889

And from git-push:

> When the command line does not specify where to push with the <repository> argument, branch.*.remote configuration for the current branch is consulted to determine where to push. If the configuration is missing, it defaults to origin.

I've found that if there's no remote named "origin" it pushes to the
first remote. Or so it seems:

https://gist.github.com/x-yuri/888261d182fdab92040760138ea10a22

(2) I wonder if the documentation should be amended...

Regards,
Yuri

Re: push.default and "git push"

[Junio C Hamano]

Yuri Kanivetsky <yuri.kanivetsky@gmail.com> writes:

> (1) What does "remember" exactly mean?

Because your matching push updates only the branches that exist at
the receiving repository, you do not have to remember in your head
which branches you want to keep updating over there and write them
on your command line (i.e. "git push there this-branch" to update
"this-branch" in "there" repository).

You do not have to ask your configuration file to remember
(i.e. [remote "there"] push = refs/heads/this-branch), either.

Without having to make an active effort to "remember" on your side,
"git push there" would notice that they have this-branch (because
you pushed there the last time to create it) and you have updated
this-branch on your end, and update that branch.

That is what the verb "remember" refers to in that sentence.

Re: push.default and "git push"

[Yuri Kanivetsky]

It's been a while :) but... I've been researching some aspects of how
git works, and stumbled upon this issue again.

I came up with the following explanation (of how `push.default =
matching` works):

> In this mode `git push` pushes matching branches, i.e. all local branches that exist in a remote, to their remote counterparts (if there's a local branch `ba` and a remote branch `origin/ba`, it pushes `ba` to `origin/ba`):
>
> * First it chooses a remote:
>
>   * if the current branch has an upstream, it chooses the remote the upstream points to
>
>   * else if there's only one remote, it chooses this only remote
>
>   * else it chooses `origin` if it exists
>
>   * otherwise it fails
>
> * Then it pushes matching branches to the remote.
>
> * If the upstream of the current branch is in the local repo, there can be no matching branches by definition (there can't be 2 branches with the same name in a repository).
>
> * It never chooses a non-matching branch, even if it's an upstream. If `ba` has an upstream `origin/ba2` and there's `origin/ba`, it will choose `origin/ba`.

More in the following gist:

https://gist.github.com/x-yuri/0ac53cb7999b3b0352c1ec0ac8f5f4cc

The description given in the documentation:

> matching - push all branches having the same name on both ends. This makes the repository you are pushing to remember the set of branches that will be pushed out (e.g. if you always push maint and master there and no other branches, the repository you push to will have these two branches, and your local maint and master will be pushed there).

One can sort of make an argument that the remote repository kind of
remembers the branches you push to it, but... if you delete the local
branch that you just pushed, does that make the remote repository
forget that you pushed the branch?.. The analogy is flawed. And
confusing, because it's not at all clear that the state is stored "by
the list of the branches".

Also a lot of aspects of how `push.default = matching` works are left out.

Regards,
Yuri