Merge branch '6.4' into 7.0

* 6.4:
  Remove subtree split checks
  Revert "minor #54653 Auto-close PRs on subtree-splits (nicolas-grekas)"

Author: fabpot

.gitattributes

@@ -1,3 +1,4 @@
 /Tests export-ignore
 /phpunit.xml.dist export-ignore
-/.git* export-ignore
+/.gitattributes export-ignore
+/.gitignore export-ignore