The Git Commands You Wish You Always Had
Recently I wanted to do a bulk cleanup on some GitHub repositories I am responsible for, like deleting old branches that have already been merged into the default branches. I first considered performing it through the GitHub API, but then I decided to try doing it via Git itself.
After I had begun dabbling with a few wrapper scripts, I suddenly remembered something which massively simplified my strategy: Git Aliases. These are Git commands you can define yourself, either via CLI or in the Gitconfig file.
With this article, I want to introduce what I learned about Git aliases – and in the process, you get all the aliases I defined for my cleanup 😉
Defining Shortcuts
Many articles about Git aliases explain only the shortcut side.
They show e.g. how you can abbreviate git checkout to git co by running git config --global alias.co checkout.
As an alternative to the CLI command, you can add this section to your ~/.gitconfig file:
[alias]
co = checkout
Nowadays, with the Git plugin of oh-my-zsh, I don't feel there is a great need for such shortcuts. Let's instead talk about actual custom commands:
With Parameters
If you use an exclamation mark before your command, you can run any Shell command you want, even with parameters.
The following example will let you do e.g. git cat 2eea778 package.json to get the file contents of a file at a certain revision:
[alias]
; Output file contents from any revision
; See https://stackoverflow.com/a/54819889/6435726
cat = !git show "$1:$2"
Pass It On
Piping output into other commands is available out of the box.
Executing multiple commands is just a && away.
You may want to break your command into multiple lines: Do so by wrapping your command into quotes and prepending every new line with a backslash.
; What is the default branch of this repo?
; The first command asks the remote if the default branch was changed.
default-branch = "! \
git remote set-head origin -a > /dev/null \
&& git rev-parse --abbrev-ref origin/HEAD \
| sed 's#origin/##'"
You can also use subshells:
; Switch to the default branch.
switch-default = !git switch $(git default-branch)
Escaping Can Be Tricky
If you want to have a literal backslash in the resulting Shell command, you have to escape it.
Pay attention to the grep patterns in the following aliases:
Every double backslash of this pattern becomes a single backslash when Git passes the command to the Shell.
; Which branches have been merged into the default branch on the remote?
; For safety, manually add names of long-lived branches to the grep pattern.
remotely-merged-branches = "! \
git branch --all --merged $(git default-branch) \
| { grep -vE '^\\*|(\\b($(git default-branch)|develop|main|master|quality)\\b)' || true; } \
| sed 's#remotes/origin/##'"
; Which local branches are not present on the remote (but were once)?
; NOTE: `git remote prune origin` only deletes local snapshots
; of remote branches that were deleted on the remote.
; See https://stackoverflow.com/a/48820687/6435726
; It will not delete local branches where the remote branch is "gone".
; This command finds these local branches.
local-branches-without-remote = "! \
git remote prune origin && \
git branch --list --format '%(if:equals=[gone])%(upstream:track)%(then)%(refname)%(end)' \
| awk NF \
| sed 's#refs/heads/##'"
I think these are the dangers of every templating language:
You have to account for special characters - but if these special characters happen to be special in someone else's language, things can become unexpectedly complicated.
(Think about Makefiles and $(variables) vs. $$variables in rules.)
Parameters Pt. 2: Default Values
As with any other Shell function, you can not only have positional parameters but you can also give them default values.
The following alias has a delete flag that defaults to the safe behavior, but you can overwrite it with git delete-local-branches-without-remote -D:
; Delete local branches that are not present on the remote
; (safely, including warnings).
; You can ignore the warnings by passing "-D" as a parameter.
; NOTE: `git remote prune origin` only deletes local snapshots
; of remote branches that were deleted on the remote.
; It will not delete local branches where the remote branch is "gone".
delete-local-branches-without-remote = "! \
git local-branches-without-remote \
| xargs -I {} git branch ${1:-'-d'} {}"
This last alias is what finally deletes the remote branches I wanted to target.
It also demonstrates nicely how you can use xargs to run every Shell command as if it was capable of handling stdin natively:
; Delete branches on the remote which were merged.
push-delete-remotely-merged-branches = "! \
git switch-default && \
git remotely-merged-branches \
| xargs -I {} git push origin --delete {}"
Debugging
If you encounter an error message, you can increase the verbosity with this environment variable:
export GIT_TRACE=1
Deactivate it afterward by closing your terminal session or explicitly with unset GIT_TRACE.
Bringing It All Together: Multiple Repositories
As a developer, chances are high you have more than just one Git repository on your machine. For many everyday use cases (like keeping all your local clones up-to-date), I have been using git-repo-updater with a lot of success and ease.
But now I discovered I can use it to execute arbitrary commands (and also Git aliases 😉) in multiple Git repos.
With the following Shell function I am wrapping gitup for convenience:
# Execute a Git command on all Git repositories
# $1: Path with Git repositories in subdirectories
# Rest of parameters: Git command (e.g. "status")
function git-xargs() {
local filepath="$1"
# shellcheck disable=SC2116
gitup --depth -1 "$filepath" --exec "git $(echo "${@:2}")"
}
And now I can finally clean up all branches with just one command (and quite pretty output):
git-xargs ~/Documents push-delete-remotely-merged-branches
git-xargs ~/Documents delete-local-branches-without-remote