git_auto_update: Allowed omiting of sign check

roles/git_auto_update/templates/update.sh

@@ -15,11 +15,12 @@ if [ ! -d .git ]; then
   git clone "$REPO" "$DEST";
 fi
 
-gpg --quiet --keyserver eu.pool.sks-keyservers.net --recv "$GPG_FINGERPRINT";
+[ -z "$GPG_FINGERPRINT" ] ||
+  gpg --quiet --keyserver eu.pool.sks-keyservers.net --recv "$GPG_FINGERPRINT";
 
 git fetch --tags > /dev/null;
 TAG=$(git tag --list | grep "^$PREFIX" | sort -r | head -n 1);
-if git verify-tag --raw "$TAG" 2>&1 | grep " VALIDSIG $GPG_FINGERPRINT " > /dev/null; then
+if [ -z "$GPG_FINGERPRINT" ] || git verify-tag --raw "$TAG" 2>&1 | grep " VALIDSIG $GPG_FINGERPRINT " > /dev/null; then
   git reset --hard;
   git checkout -q "$TAG";
   chown -R "$DEST_USER:$DEST_GROUP" .;