sync-branch.sh

#!/bin/bash

# example usage:
# $ sync-branch origin/production production

# issues:
# * what if files have been modified? handle pull failure.

# http://stackoverflow.com/a/12791408/1596013
# http://stackoverflow.com/a/12142066/1596013
# http://stackoverflow.com/a/10520718/1596013
# http://stackoverflow.com/a/5168129/1596013

# exit statuses
EXIT_SUCCESS=0
EXIT_NOTGIT=1
EXIT_INVALID=2
EXIT_WRONGBRANCH=3
EXIT_AHEAD=4

# must be a git directory
git status >/dev/null 2>&1
if [ $? != 0 ]; then
	echo 'this is not a git directory.'
	exit $EXIT_NOTGIT
fi

# config
REMOTE="${1%/*}"
BRANCH_REMOTE="${1#*/}"
BRANCH_LOCAL="$2"
BRANCH_CURRENT=`git rev-parse --abbrev-ref HEAD`
echo "syncing ($BRANCH_LOCAL) with ($REMOTE/$BRANCH_REMOTE)"

# exit if invalid branches
git show-branch "$REMOTE/$BRANCH_REMOTE" >/dev/null 2>&1
if [ $? != 0 ]; then
	echo "error: invalid remote branch ($1)"
	exit $EXIT_INVALID
fi
git show-branch "$BRANCH_LOCAL" >/dev/null 2>&1
if [ $? != 0 ]; then
	echo "error: invalid local branch ($2)"
	exit $EXIT_INVALID
fi

# exit if wrong branch checked out
if [ $BRANCH_CURRENT != $BRANCH_LOCAL ]; then
	echo "error: wrong branch checked out ($BRANCH_CURRENT). expecting ($BRANCH_LOCAL)"
	exit $EXIT_WRONGBRANCH
fi

# find out where we are
git fetch
AHEAD=`git log $REMOTE/$BRANCH_REMOTE..HEAD --oneline`
BEHIND=`git log HEAD..$REMOTE/$BRANCH_REMOTE --oneline`

# exit if we're locally ahead of remote
if [ "$AHEAD" ]; then
	echo 'AHEAD:'
	echo $AHEAD
	echo 'error: local ahead of remote'
	exit $EXIT_AHEAD
fi

# if we're behind, lets pull.
if [ "$BEHIND" ]; then
	echo 'BEHIND:'
	echo $BEHIND
	echo 'local behind remote. pull...'
	git pull $REMOTE $REMOTE_BRANCH
else
	echo 'up-to-date. nothing to do.'
fi

# win!
echo 'success'
exit $EXIT_SUCCESS