Checkout previous Git branch

checkout_previous_branch.sh

#!/bin/sh

## Checks out the branch with the name recorded in the .PREVIOUS_BRANCH file
## in the working directory. To use this script, you should be using the 
## post-checkout hook that creates such a file.

if [ ! -f ./.PREVIOUS_BRANCH ]
then
	echo "No previous branch has been recorded. You're probably not using the post-checkout hook."
	exit 1
fi

previous_branch=`cat ./.PREVIOUS_BRANCH`
git checkout ${previous_branch}

post-checkout.sh

#!/bin/sh

## When the branch changes, record the name of the previously checked-out branch
## in a file called .PREVIOUS_BRANCH in the working directory.
## To use this script, place it in your .git/hooks directory, with the name "post-checkout".
## You should probably edit your .git/info/exclude file to ignore .PREVIOUS_BRANCH, too.

previous_ref=$1

heads_matching_previous_ref=`grep -r $previous_ref .git/refs/heads/*`

# http://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch#comment9751841_1593487
current_branch=`git symbolic-ref HEAD 2>/dev/null | cut -d"/" -f 3`

# the previous branch is the branch whose HEAD matches the previous ref,
# which is not the current branch (so that we ignore a newly forked & checked out branch)
# we assume that the user won't have 3 or more branches with the same HEAD
for head in $heads_matching_previous_ref
do
	# heads are of the form .git/refs/heads/<branch>:<SHA>
	branch=`echo ${head} | sed 's/\.git\/refs\/heads\/\(.*\)\:.*/\1/'`

	if [ ${branch} != ${current_branch} ]
	then
		echo ${branch} > ./.PREVIOUS_BRANCH
		break
	fi
done