added warning if index already existis

dge_workflow/dge_utils.sh

@@ -414,6 +414,12 @@ dge_create_star_index(){
     fi
 
     export star_index="${igenome}/Sequence/StarIndex"
+
+    ## stop if index exists already
+    if [ -d "$star_index" ]; then
+        echo "Error: Index directory ${star_index} already exists." >&2 ; return;
+    fi
+
     chmod +w $(dirname ${star_index})
 
     mailme "${project}: creating STAR index in ${star_index}"