Merge branch 'fix-CLEANDATE' into 'master'

Use git rev-list --first-parent when checking out git repositories when CLEANDATE is set

See merge request !71

generic/fetch.sh

@@ -36,7 +36,7 @@ if [ -e $PACKAGE/$OS-$ARCH/git-sources.txt ]; then
 			if [ -n "${CLEANDATE+set}" ]; then
 				git clone -b $branch $GIT_BASEURL/$group/$repo.git src/$repo-$branch
 				(cd src/$repo-$branch
-					git checkout `git rev-list -n 1 --before="$CLEANDATE" $branch`
+					git checkout `git rev-list -n 1 --first-parent --before="$CLEANDATE" $branch`
 					git submodule update --init --recursive)
 			else
 				git clone --recursive -b $branch $GIT_BASEURL/$group/$repo.git src/$repo-$branch