Keep your forked repository in sync with upstream

syncrepository.sh

#
#	Script to keep github forked repository in sync with upstream.
#	synchronizes branches which names match between REMOTE and UPSTREAM
#
#	Uses the following shell variables, maybe passed on the command line
#	path=/path/to/git/dir upstream=upstream_repo remote=origin ./syncrepository.sh
#
#	Author: Aron Podrigal <[email protected]>
#
#!/bin/bash

# repository directory
GIT_DIR=${path:-"./"}

# SET THIS TO YOUR UPSTREAM NAME
UPSTREAM=${upstream:-"upstream"}

# NMAE OF REMOTE
REMOTE=${remote:-"origin"}

# FORCE CHECKOUT WITH -f OPTION "yes/no".
# if checkout to remote branch fails and this is
# set to "no", then it will try to
# stash any local changes, and pop it afterwards
FORCE_CHECKOUT=no

# set file LOGFILE=~/sync.log to redirect stdout
LOGFILE=
# set file ERROR_LOG=~/sync_err.log to redirect stderr
ERROR_LOG=

# redirect output
[ ! -z $LOGFILE ] && exec 1>>$LOGFILE
[ ! -z $ERROR_LOG ] && exec 2>>$ERROR_LOG

# logger function
function mlog()
{
	if [ ! -z ${!2} ]; then
		echo "[`date`] $1" >> ${!2}
	else
		if [ "$2" = "ERROR_LOG" ]; then
			echo "[`date`] $1" >&2
		else
			echo "[`date`] $1"
		fi
	fi
}

cd $GIT_DIR || exit 1

git fetch || { mlog "Couldn't fetch remotes. terminating" "ERROR_LOG"; exit 1; }

UPSTREAM_BRANCHES=`git branch --list -r $UPSTREAM/* |awk '{sub(/^'$UPSTREAM'\//,"",$1); print $1}'`
REMOTE_BRANCHES=`git branch --list -r $REMOTE/* |awk '{sub(/^'$REMOTE'\//,"",$1); print $1}'`

if [ -z $UPSTREAM_BRANCHES ]; then
	mlog "NOTICE: no upstream branches found for '$UPSTREAM'." "LOGFILE"
fi


# initialize stashed to false
stashed=1

for branch in $UPSTREAM_BRANCHES; do
	remote_exists=1;
	
	for remote_b in $REMOTE_BRANCHES; do
		if [ $remote_b = $branch ]; then
			remote_exists=0
			break
		fi
	done
	
	if [ $remote_exists ]; then
		# checkout the remote branch and merge in upstream
		git checkout $REMOTE/$branch
		if [ $? -ne 0 ]; then
			mlog "git checkout returned error" "ERROR_LOG"
			if [ $stashed -eq 0 ]; then
				mlog "working directory was previously stashed, so we're forcing checkout" "LOGFILE"
				git checkout $REMOTE/$branch -f || { mlog "couldn't checkout ${REMOTE}/${branch}, terminating." "ERROR_LOG"; exit 1; }
			else
				mlog "trying to stash before checkout.." "LOGFILE"
				git stash || { mlog "could not stash either terminating" "ERROR_LOG"; exit 1; }
				# keep track that we've stashed away, so we'll pop afterwards
				stashed=0
				git checkout $REMOTE/$branch || { mlog "couldn't checkout ${REMOTE}/${branch}, terminating." "ERROR_LOG"; exit 1; }
			fi
		fi
		
		git merge --ff $UPSTREAM/$branch || { mlog "'git merge --ff ${UPSTREAM}/${branch}' into ${REMOTE}/${branch} failed." "ERROR_LOG"; }
		git push $REMOTE HEAD:$branch &&  mlog "'git merge --ff ${UPSTREAM}/${branch}' into ${REMOTE}/${branch} successfuly pushed to remote." "LOGFILE" \
						|| { mlog "'git merge --ff ${UPSTREAM}/${branch}' into ${REMOTE}/${branch} failed to push to remote." "ERROR_LOG"; }
	else
		mlog "New upstream branch '$branch' found" "LOGFILE"
		# push to remote
		git push $REMOTE $UPSTREAM/$branch:refs/heads/$branch &&  mlog "'git push $REMOTE $UPSTREAM/$branch:refs/heads/$branch' <New Branch> successful." "LOGFILE" \
								|| { mlog "'git push $REMOTE $UPSTREAM/$branch:refs/heads/$branch' <New Branch> failed." "ERROR_LOG"; }
	fi
done	

if [ $stashed -eq 0 ]; then
	git stash pop
fi