Git post-commit hook to create a branch automatically when commiting from a detached HEAD

git-post-commit-branch-detached

#!/bin/sh
#
# Git post-commit hook to create a branch automatically when commiting from a
# detached HEAD.
#
# Install in your repo as .git/hooks/post-commit and make it executable.
#
# Ben Cohen, December 2017.

set -e

BRANCH=`git rev-parse --abbrev-ref HEAD`

if [ "$BRANCH" = "HEAD" \
     -a ! -e "$GIT_DIR/rebase-apply" \
     -a ! -e "$GIT_DIR/rebase-merge" ]
then
    # Detached HEAD and this is not a rebase
    COMMIT=`git rev-parse --verify --short HEAD`
    BNAME=`date +"DH-%Y-%m-%d-$COMMIT"`
    
    echo "Commit on detached HEAD: creating branch $BNAME."
    echo '(Use "branch -m <newbranch>" to rename it.)'
    echo

    git checkout -b $BNAME
fi