pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,5 +1,5 @@
 * Delete this list before clicking CREATE PULL REQUEST
-* Make sure you're using a special branch just for this pull request. (Sometimes people unknowingly update their submission branch, which updates the pull request with other changes.)
+* Make sure you're using a special branch just for this pull request. (Sometimes people unknowingly use a default branch, then later update that branch, which updates the pull request with the other changes if it hasn't been merged yet.)
 * Do NOT update the version number in the file. (This just causes conflicts.)
 * Do add your name to the list of contributors. (Don't worry about the formatting.) I'll try to remember to add it if you don't, but I sometimes forget as it's an extra step.