I maintain Debian packages for several projects which are hosted on GitHub. I have a master packaging branch containing both upstream’s code, and my debian/ subdirectory containing the packaging control files. When upstream makes a new release, I simply merge their release tag into master: git merge 1.2.3 (after reviewing the diff!).

Packaging things for Debian turns out to be a great way to find small bugs that need to be fixed, and I end up forwarding a lot of patches upstream. Since the projects are on GitHub, that means forking the repo and submitting pull requests. So I end up with three remotes:

origin
the Debian git server
upstream
upstream’s GitHub repo from which I’m getting the release tags
fork
my GitHub fork of upstream’s repo, where I’m pushing bugfix branches

I can easily push individual branches to particular remotes. For example, I might say git push -u fork fix-gcc-6. However, it is also useful to have a command that pushes everything to the places it should be: pushes bugfix branches to fork, my master packaging branch to origin, and definitely doesn’t try to push anything to upstream (recently an upstream project gave me push access because I was sending so many patches, and then got a bit annoyed when I pushed a series of Debian release tags to their GitHub repo by mistake).

I spent quite a lot of time reading git-config(1) and git-push(1), and came to the conclusion that there is no combination of git settings and a push command that do the right thing in all cases. Candidates, and why they’re insufficient:

git push --all
I thought about using this with the remote.pushDefault and branch.*.pushRemote configuration options. The problem is that git push --all pushes to only one remote, and it selects it by looking at the current branch. If I ran this command for all remotes, it would push everything everywhere.
git push <remote> : for each remote
This is the “matching push strategy”. It will push all branches that already exist on the remote with the same name. So I thought about running this for each remote. The problem is that I typically have different master branchs on different remotes. The fork and upstream remotes have upstream’s master branch, and the origin remote has my packaging branch.

I wrote a perl script implementing git push-all, which does the right thing. As you will see from the description at the top of the script, it uses remote.pushDefault and branch.*.pushRemote to determine where it should push, falling back to pushing to the remote the branch is tracking. If won’t push something when all three of these are unspecified, and more generally, it won’t create new remote branches except in the case where the branch-specific setting branch.*.pushRemote has been specified. Magit makes it easy to set remote.pushDefault and branch.*.pushRemote.

I have this in my ~/.mrconfig:

git_push = git push-all

so that I can just run mr push to ensure that all of my work has been sent where it needs to be (see myrepos).

#!/usr/bin/perl

# git-push-all -- intelligently push most branches

# Copyright (C) 2016 Sean Whitton
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Prerequisites:

# The Git::Wrapper, Config::GitLike, and List::MoreUtils perl
# libraries.  On a Debian system,
#     apt-get install libgit-wrapper-perl libconfig-gitlike-perl \
#         liblist-moreutils-perl

# Description:

# This script will try to push all your branches to the places they
# should be pushed, with --follow-tags.  Specifically, for each branch,
#
# 1. If branch.pushRemote is set, push it there
#
# 2. Otherwise, if remote.pushDefault is set, push it there
#
# 3. Otherwise, if it is tracking a remote branch, push it there
#
# 4. Otherwise, exit non-zero.
#
# If a branch is tracking a remote that you cannot push to, be sure to
# set at least one of branch.pushRemote and remote.pushDefault.

use strict;
use warnings;
no warnings "experimental::smartmatch";

use Git::Wrapper;
use Config::GitLike;
use List::MoreUtils qw{ uniq apply };

my $git = Git::Wrapper->new(".");
my $config = Config::GitLike->new( confname => 'config' );
$config->load_file('.git/config');

my @branches = apply { s/[ \*]//g } $git->branch;
my @allBranches = apply { s/[ \*]//g } $git->branch({ all => 1 });
my $pushDefault = $config->get( key => "remote.pushDefault" );

my %pushes;

foreach my $branch ( @branches ) {
    my $pushRemote = $config->get( key => "branch.$branch.pushRemote" );
    my $tracking = $config->get( key => "branch.$branch.remote" );

    if ( defined $pushRemote ) {
        print "I: pushing $branch to $pushRemote (its pushRemote)\n";
        push @{ $pushes{$pushRemote} }, $branch;
    # don't push unless it already exists on the remote: this script
    # avoids creating branches
    } elsif ( defined $pushDefault
              && "remotes/$pushDefault/$branch" ~~ @allBranches ) {
        print "I: pushing $branch to $pushDefault (the remote.pushDefault)\n";
        push @{ $pushes{$pushDefault} }, $branch;
    } elsif ( !defined $pushDefault && defined $tracking ) {
        print "I: pushing $branch to $tracking (probably to its tracking branch)\n";
        push @{ $pushes{$tracking} }, $branch;
    } else {
        die "E: couldn't find anywhere to push $branch";
    }
}

foreach my $remote ( keys %pushes ) {
    my @branches = @{ $pushes{$remote} };
    system "git push --follow-tags $remote @branches";
    exit 1 if ( $? != 0 );
}

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