Is there a way to trigger a hook after a new branch has been checked out in Git?

Question

Is there a way to trigger a hook after a new branch has been checked out in Git?

Answer 1

The post-checkout hook receives three parameters:

1. Ref of previous HEAD
2. Ref of new HEAD
3. Whether this is a file checkout (0) or branch checkout (1)

You can use the fact that a branch created from the current HEAD will have the same value for parameters 1 and 2.

cat > .git/hooks/post-checkout <<"EOF"
if [ "$3" == "0" ]; then exit; fi
if [ "$1" == "$2" ]; then 
  echo "New branch created. (Probably)."
fi
EOF

chmod u+x .git/hooks/post-checkout

Limitations:

• Checking out an existing branch which happens to be at the same HEAD as the current HEAD will fool it.
• Creating a new branch not from the current HEAD will not be detected.