

Git hooks

Git hooks help you to automate things to have less work by executing custom scripts at certain Git events.

Create a hook

Git hooks are located in the directory .git/hooks of any Git repository.

From the start there are some sample scripts that you can check out.

Modify the commit message

Create in this directory the file prepare-commit-msg with the follwoing content:

#!/bin/sh

# Get commit info
COMMIT_MSG_FILE=$1

# Create a text that will be pushed to the commit message file
PREPARE_COMMIT_MSG="# Summarize changes in around 50 characters or less

# More detailed explanatory text, if necessary.
# Wrap it to about 72 characters or so.
# A blank line to the summary is necessary to get a paragraph!
#
# More info if needed (again, don't forget one blank line!)
# - Lists/Bullet points are okay, leave a line between each bullet
#   point and one above the list
#
# For issue trackers, put references to them at the bottom, like:
# (don't forget one blank line!)
# Resolves: #123
# See also: #456, #789
#
# More info at: https://chris.beams.io/posts/git-commit/"

# Every line that begin with "#" will be forgotten when committed
echo "$PREPARE_COMMIT_MSG" > $1

(If you are on Linux run chmod +x prepare-commit-msg to make the file executable)

If you now try to make a commit (git commit or git commit -S) this will come always up and your input will result in the commit message.

Bug

If you would run git commit -m "test" The commit message results in the commented text! This needs to be fixed before it can be used without pain!

(Safety-)Checks before a commit

With the Git hook file pre-commit you can make safety checks before the commit is made. The pre-commit script is executed every time you run git commit before Git asks the developer for a commit message or generates a commit object.

This is really useful when you do not to push code that fails a test for example.

The only thing you need to do is exit the script with exit 0 if all tests resulted in no failures else return exit 1 and the commit will not be made.

#!/bin/sh

# Run tests
npm run test

# If no error (test ran successful) exit with 0 and go on with commit process
exit 0

Hint

This example is used by the maintainer of this repository to only let commits through that at least pass all tests.

Update documentation after any post

You can use the Git hook file post-commit to execute a custom script after a commit is made.

A useful example could be to update to documentation:

#!/bin/sh

# Create documentation
npm run docs

# Move documentation to custom place (documentation repository)
rm -r ../IliasBuddyDesktopDocs/*
cp -r ./docs/site/* ../IliasBuddyDesktopDocs/

# Ask if the current progress should be pushed
read -p "Do you want to push the current progress " -n 1 -r
if [[ $REPLY =~ ^[Yy]$ ]]
then
    # Commit and push the current progress
    git push
else
    # Else exit
    exit 0
fi

# If user pushed current progress commit/push updated documentation
cd ../IliasBuddyDesktopDocs/
git add .

# Ask if everything should be pushed
read -p "Do you want to push the documentation " -n 1 -r
if [[ $REPLY =~ ^[Yy]$ ]]
then
    # Commit and push current documentation
    git commit -S -m "Updated to latest master"
    git push
fi

Bug

This example is not working on Windows computers because read can't be found. A port of the GNU utility read for Windows is needed (I couldn't find any port myself).

Hint

This example is used by the maintainer of this repository to automatically update the documentation. Do not forget that you need to git push the initial commit. The documentation is only pushed because there is sadly no post-push hook in Git.