This content originally appeared on DEV Community and was authored by Brodan
In yet another instance of a blog post inspired by a single tweet, this post will offer a very basic introduction to git hooks (commit hooks, to be specific).
The Tweet
Challah Bäck Girl@emgrasmeder
a post-commit hook that amends your commit message with ", hopefully"22:29 PM - 04 May 2021
I saw this on my timeline earlier today, had a good chuckle, and then realized that despite knowing about git hooks for a long time, I've never actually written one. I decided to fix that by writing a dead simple hook that would recreate the aforementioned Tweet.
The Code
Start by initializing a new git repo as such:
cd /tmp && mkdir hook-testing
cd hook-testing
git init
git actually generates a number of sample hooks when you initialize a repo. You can see them all by running ls .git/hooks/.
If you look closely, there's a hook named prepare-commit-msg.sample. How convenient! This hook, once enabled, will run every time a git commit command is run when working in this repo.
You can read more about this hook in the githooks Documentation.
In order for git to actually pick up and run a hook, the .sample extension must be removed:
mv .git/hooks/prepare-commit-msg.sample .git/hooks/prepare-commit-msg
Open .git/hooks/prepare-commit-msg in an editor and feel free to look at the examples. Then replace it all with the following:
#!/bin/sh
COMMIT_MSG_FILE=$1
COMMIT_SOURCE=$2
DREAM=", hopefully"
if [[ "$COMMIT_SOURCE" == "message" ]]
then
echo `cat $COMMIT_MSG_FILE`$DREAM > $COMMIT_MSG_FILE
fi
I kept this hook pretty simple since my shell-scripting abilities are lackluster.
git passes three arguments into the prepare-commit-msg hook, but we only care about the first two:
-
$1is the name of the file that contains the commit log message. We will append our optimistic message to this file. -
$2is the source of the commit message and is set according to how the commit is being generated (such as in amerge,squash, etc, or just a regular oldcommit).
In this case, the hook is only going to run if the commit source is "message", meaning that the commit was made using the -m flag. Feel free to modify this to your liking.
In order to see it in action, we need to commit something:
git commit --allow-empty -m "adding an empty commit"
[master 1031a40] adding an empty commit, hopefully
As you can see above, the commit message was updated to include the ", hopefully" message. You can run git log to see it again if you want to double-check.
The Conclusion
I hope you found this post informative and entertaining. The hook itself is very simple but I actually learned a log about git internals while working on it.
If you'd like to see the other posts I've written that were inspired entirely by Tweets, consider these:
- Build John Mayer's Customer Service Line with Twilio Voice and Python
- Waifu MMS Bot - Send a Selfie, Receive a Waifu
Thanks for reading!
This content originally appeared on DEV Community and was authored by Brodan
Brodan | Sciencx (2021-05-06T19:43:27+00:00) “, hopefully” – An Intro to Git Hooks. Retrieved from https://www.scien.cx/2021/05/06/hopefully-an-intro-to-git-hooks/
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