git: Add git pushall alias

`git pushall` (aliased to gpa) will push the current branch to each
connected remote of the repository.

So, if you have gitlab, github and keybase connected as remotes, it will
push to each one in return. As with the normal push command, you can
specify which branch to push ('master', 'develop', ..) after the
command, or use `--all` to push all branches at once.

git/.config/git/config

@@ -11,6 +11,8 @@
   ignore        = "!gitignore -f"
   pushmerge     = "push -o merge_request.merge_when_pipeline_succeeds" # see https://docs.gitlab.com/ce/user/project/push_options.html#merge-when-pipeline-succeeds-alias
   last          = "diff HEAD~ HEAD"
+  # push to all connected remotes
+  pushall       = "!git remote | xargs -L1 -I R git push R"
 [commit]
   # sign commits as me
   gpgsign       = true

git/.config/sh/alias.d/git.sh

@@ -45,6 +45,7 @@ alias gpn='git push --dry-run'
 alias gp='git push'
 alias gpf!='git push --force'
 alias gpm='git pushmerge'
+alias gpa='git pushall'
 
 alias grv='git remote -v'