mock-build.sh: minor improvements

.local/scripts/el/mock-build.sh

@@ -8,20 +8,20 @@ if (! command -v mock > /dev/null) || (! groups | grep 'mock' > /dev/null); then
     exit 1
 fi
 
-if [[ -z $1 ]]; then
+if [[ -z "${1:-}" ]]; then
     echo 'Need a SOURCES directory.'
     exit 1
 fi
-if [[ ! -d $1 ]]; then
+if [[ ! -d "$1" ]]; then
     echo "'$1' is not a directory"
     exit 1
 fi
 
-if [[ -z $2 ]]; then
+if [[ -z "${2:-}" ]]; then
     echo 'Need an RPM SPEC file.'
     exit 1
 fi
-if [[ ! -f $2 ]]; then
+if [[ ! -f "$2" ]]; then
     echo "'$2' is not a file"
     exit 1
 fi
@@ -37,14 +37,15 @@ if [[ ! -d "/var/lib/mock/$MOCK_ROOT" ]]; then
     mock --root "$MOCK_ROOT" --init
 fi
 
+additional_args=( "$@" )
 # shellcheck disable=SC2086
 time mock \
-    $3 \
+    "${additional_args[@]:2}" \
     --isolation nspawn \
-    --root $MOCK_ROOT \
-    --resultdir $MOCK_OUT \
-    --sources $1 \
+    --root "$MOCK_ROOT" \
+    --resultdir "$MOCK_OUT" \
+    --sources "$1" \
     --no-cleanup-after \
     --buildsrpm \
-    --spec $2 \
+    --spec "$2" \
     --rebuild