#!/bin/bash
# patchsync: Synchronize a branch with a patch (e.g., acls.diff and rsync-acl).
# usage: patchsync <staging> {'' | --dry-run} [branch | patch]
# <staging>: the staging directory, containing a shell script "settings" and an optional rsync filter file "filter"
#     "settings" must contain:
#         - $trunk, $patch, $branch paths interpreted relative to the staging dir
#         - shell function do_diff: trunk, branch => patch
#             e.g., for rsync: diff -uprN trunk branch | sed -re 's/^(\+\+\+|---) ([^\t]+).*$/\1 \2/' | grep -v '^diff' >patch
#         - shell function do_patch: branch copied from trunk, patch => branch
#             e.g., for rsync: patch --no-backup-if-mismatch -d branch/ -p1 <patch
# --dry-run: don't note anything
# branch | patch: overwrite the specified thing in case of a conflict (e.g., on the first run)

set -e

staging="$1"
if ! [ -r "$staging/settings" ]; then
	echo "Specify a staging directory containing a settings file!" 1>&2
	exit 1
fi
cd "$staging"

dryrun="$2"
whichtochange="$3"
CP2t=(cp2 --del)
CP2in=("${CP2t[@]}" --filter='. filter' --delete-excluded)
CP2out=("${CP2t[@]}" --filter='. filter' --no-t --checksum) # be nice to mtimes
export LC_COLLATE="C"

. settings

echo "Copying in, checking for changes..."
"${CP2in[@]}" --link-dest=../trunk-save -i "$trunk/" trunk/
diff -r trunk{-save,} >/dev/null || trunkch=ch
"${CP2in[@]}" --link-dest=../branch-save -i "$branch/" branch/
diff -r branch{-save,} >/dev/null || branchch=ch
cp2 --link-dest=../patch-save -i "$patch" patch
diff -r patch{-save,} >/dev/null || patchch=ch
echo "Done."

if [ $trunkch ] || [ $branchch ] || [ $patchch ]; then
	# Something changed.
	# Update either branch or patch, whichever didn't change.
	# If trunk changes, update branch, not patch.
	if [ "$whichtochange" == 'branch' ] || ! [ $branchch ]; then
		echo "Updating branch..."
		"${CP2t[@]}" trunk/ branch/
		do_patch
		echo "Done."
		copyout=1
	elif [ "$whichtochange" == 'patch' ] || ! [ $patchch ]; then
		echo "Updating patch..."
		do_diff
		echo "Done."
		copyout=1
	else
		echo "Conflict: both branch and patch changed!"
		echo "Run patchsync <staging> <dry-run> [branch | patch] to"
		echo "update the specified area from the others."
		exit 1
	fi
else
	# Easy case
	echo "Nothing changed."
fi

if [ $copyout ]; then
if ! [ $dryrun ]; then
	! [ -e lock ] || { echo "Locked!  Please fix!"; exit 1; }
	echo "patchsync lock file pid $$ date $(date)" >lock
	
	echo "Copying out..."
	"${CP2out[@]}" -i branch/ "$branch/"
	cp2 -i --checksum patch "$patch"
	echo "Done."
	echo "Noting..."
	for i in trunk branch patch; do
		rm -rf $i-save
		mv $i{,-save}
	done
	echo "Done."
	
	rm lock
else
	echo "Dry run; no action.  You can inspect the results if you want."
	echo "Fake copying out..."
	"${CP2out[@]}" -in branch/ "$branch/"
	cp2 -in --checksum patch "$patch"
	echo "Done."
fi
fi

exit 0