contrib: show pull # in prompt for github-merge script

contrib/devtools/github-merge.sh

@@ -136,6 +136,9 @@ else
   echo "Dropping you on a shell so you can try building/testing the merged source." >&2
   echo "Run 'git diff HEAD~' to show the changes being merged." >&2
   echo "Type 'exit' when done." >&2
+  if [[ -f /etc/debian_version ]]; then # Show pull number in prompt on Debian default prompt
+      export debian_chroot="$PULL"
+  fi
   bash -i
   read -p "Press 'm' to accept the merge. " -n 1 -r >&2
   echo