File notification and JSON output fixes (#281)

* File notification and JSON output fixes

* Truncate notify file(s) on first write and then append

* Strip wrapping double quotes from Dockcheck update tempcsv variable before jsonification

* Eliminate separate truncate step

notify_templates/notify_file.sh

@@ -1,5 +1,5 @@
 ### DISCLAIMER: This is a third party addition to dockcheck - best effort testing.
-NOTIFY_FILE_VERSION="v0.1"
+NOTIFY_FILE_VERSION="v0.2"
 #
 # Leave (or place) this file in the "notify_templates" subdirectory within the same directory as the main dockcheck.sh script.
 # If you instead wish make your own modifications, make a copy in the same directory as the main dockcheck.sh script.
@@ -13,10 +13,14 @@ trigger_file_notification() {
     UpperChannel="FILE"
   fi
 
+  FileTruncVar="${UpperChannel}_TRUNC"
   FilePathVar="${UpperChannel}_PATH"
-
   NotifyFile="${!FilePathVar:=${ScriptWorkDir}/updates_available.txt}"
 
-  echo "${MessageBody}" > ${NotifyFile}
-
+  if [[ ${!FileTruncVar:=0} -eq 0 ]]; then
+    echo "${MessageBody}" > ${NotifyFile}
+    declare -g ${FileTruncVar}=1
+  else
+    echo "${MessageBody}" >> ${NotifyFile}
+  fi
 }