octocatalog-diff: Add an IN_OCTOCATALOG_DIFF envvar passed to puppet

bin/octocatalog-diff

@@ -120,8 +120,10 @@ fi
 
 function run-octocatalog-diff {
     host=$1
-    PUPPET_FACT_DIR=$FACTS_DIR \
-    OCTOCATALOG_DIFF_CONFIG_FILE=$OCD_BASE/octocatalog-diff.config.rb \
+    env \
+      PUPPET_FACT_DIR=$FACTS_DIR \
+      OCTOCATALOG_DIFF_CONFIG_FILE=$OCD_BASE/octocatalog-diff.config.rb \
+      IN_OCTOCATALOG_DIFF=yes \
         octocatalog-diff \
           --bootstrapped-from-dir $TMPDIR/environments/$FROM \
           --bootstrapped-to-dir $TMPDIR/environments/$TO \

octocatalog-diff/octocatalog-diff.config.rb

@@ -174,7 +174,7 @@ module OctocatalogDiff
       #   specify them here. The return value must be an array.
       ##############################################################################################
 
-      # settings[:pass_env_vars] = %w(AUTH_USERNAME AUTH_TOKEN)
+      settings[:pass_env_vars] = %w(IN_OCTOCATALOG_DIFF)
 
       ##############################################################################################
       # puppet_binary