How to stop yourself from force-pushing to `master`
If you’re like me, you probably use git, and if you’re like me, you probably use git badly. Years of working on projects by myself have ingrained in me a few habits that don’t transfer well to team environments – perhaps most notably, pushing (even force-pushing) to the master branch.
This post documents the steps I’ve taken to catch myself before this happens.
Git hooks, briefly
A git hook is a program that can be run by git at various points in your git workflow. Typical examples include pre-commit
(run before making a commit) and post-checkout
(run after switching branches).
I’m not bothered by making bad commits – in fact, I often do this on purpose to rebase later. What I’m trying to do is prevent pushing these bad commits, so I make a pre-push
hook.
Complete program text1
#!/bin/bash
# don't allow --force-pushing to master branch
hook_name="hooks/$(basename $0)"
cur_branch=$(git name-rev --name-only --no-undefined --always HEAD)
push_cmd=$(ps --pid $PPID --format "command=")
protected_branches="^(master|dev|release-*|patch-*)"
forceful_flags="force|delete|-f"
affirmative="yes|y|Y"
# putting regexes in quotes makes them fail, because bash ¯\_(ツ)_/¯
if [[ "$cur_branch" =~ $protected_branches ]]; then
if [[ "$push_cmd" =~ $forceful_flags ]]; then
echo -e "${hook_name}: don't force-push to $cur_branch"
exit 1
else
echo -ne "${hook_name}: are you aware that you are on branch ${cur_branch}? "
read confirmation < /dev/tty
if [[ ! "$confirmation" =~ $affirmative ]]; then
exit 2
fi
fi
fi
exit 0
You can find the latest version of this file in my dotfiles repository.
Explanation
The code is pretty short and straightforward, but there are a few things worth explaining:
Getting the current branch name
git name-rev
exists to make getting the symbolic names of branches easy.
Reading from stdin
Git hooks are not intended to run interactively. This is a problem if you are trying to write a confirmation (“are you sure?”) program.
To circumvent this, read directly from /dev/tty
.
Checking the command-line arguments
pre-push
will be forked from the git
command that you run. With this in mind, we can pass the parent process ID to ps
and it will output the command that was run.2
Exit status
If a hook exits with a non-zero exit status, git won’t follow through with the operation. I exploit this by exiting with 1
when we don’t want to push, and 0
when we do.
To set up
To apply this hook globally, to all current and future repos:
> cd ~
> mkdir -p .config/global_git_hooks/
> git config --global core.hooksPath .config/global_git_hooks
You can name your hooks directory whatever you want; here, I chose the name .config/global_git_hooks/
. Save the file above as pre-push
in the appropriate directory.
Ensure the file is executable:
> chmod +x ~/.config/global_git_hooks/pre-push
That’s all it takes – the program will be run every time invoke git push
.
Restoring the default behaviour
Sometimes, you might want the default behaviour. No problem! cd
into the repository and edit the local config with git config core.hooksPath $GIT_DIR/hooks
. This will override your global and allow custom settings on a repo-per-repo basis.
What if I know what I’m doing and I really want to anyway?
You can skip the execution of hooks with git push --no-verify
. Best of luck with that.
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