Q: What are they?

A: Git hooks let you fire off custom scripts during your normal git workflow.

There are two kinds: client side and server side.

Client side examples:

  • do something before/after you commit
  • do something before/after you push

Server side examples:

  • can run before/after deployments
  • can reject pushes as well as output error messages back to client based on parameters you specify

In this post, I'm going to focus on the client side hooks.




Q: Where are they?

A: You can see some samples in .git/hooks in any git repository.

Tip: There are a bunch of sample files in there already with lots of useful hooks.

To use one of them, rename the .sample file so that it has no extention



Q: What can you do with them?

A: Search source code for debugger, binding.pry, console.logs

Have you ever commited a binding.pry to staging by accident? Wouldn't it be nice to grep for strings like 'binding.pry' or 'debugger' before each commit? Just use the pre-commit git hook:

.git/hooks/pre-commit

#!/bin/sh

if git-rev-parse --verify HEAD >/dev/null 2>&1; then
    against=HEAD
else
    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

for FILE in `git diff-index --check --name-status $against -- | cut -c3-` ; do
  # Check if the file contains 'debugger'
  if [ "grep 'debugger' $FILE" ]
  then
    echo $FILE ' contains debugger!'
    exit 1
  fi
done
exit


A: Auto deploy on git push

.git/hooks/post-receive

#!/bin/sh
#
## store the arguments given to the script
read oldrev newrev refname

## Where to store the log information about the updates
LOGFILE=./post-receive.log

# The deployed directory (the running site)
DEPLOYDIR=/var/www/html/simpleapp

##  Record the fact that the push has been received
echo -e "Received Push Request at $( date +%F )" >> $LOGFILE
echo " - Old SHA: $oldrev New SHA: $newrev Branch Name: $refname" >> $LOGFILE

## Update the deployed copy
echo "Starting Deploy" >> $LOGFILE

echo " - Starting code update"
GIT_WORK_TREE="$DEPLOYDIR" git checkout -f
echo " - Finished code update"

echo " - Starting composer update"
cd "$DEPLOYDIR"; composer update; cd -
echo " - Finished composer update"

echo "Finished Deploy" >> $LOGFILE


A: Run the test suite on commit; if it fails, reject commit

.git/hooks/blah

#!/bin/bash

# Stash unstaged changes before running tests
git stash -q --keep-index

# Run tests
RUN_TESTS_CMD='rspec spec/no_rails'
NUM_FAILS=`${RUN_TESTS_CMD} --format=progress | grep "example"| grep "fail"| awk {'print $3'}`

# Unstash
git stash pop -q

if [ $NUM_FAILS -ne 0 ]
then
  echo -e "Can't commit! You've broken $NUM_FAILS tests!!!"
  exit 1
else
  echo -e "All tests passed. You didn't break anything. Congrats!\n"
  exit 0
fi



Check the samples in your .git/hooks directory for more ideas!

More about customizing git hooks.