Merge branch 'js/mv-dir-to-new-directory' into maint

Merge branch 'js/mv-dir-to-new-directory' into maint

"git mv dir non-existing-dir/" did not work in some environments
the same way as existing mainstream platforms.  The code now moves
"dir" to "non-existing-dir", without relying on rename("A", "B/")
that strips the trailing slash of '/'.

* js/mv-dir-to-new-directory:
  git mv: do not keep slash in `git mv dir non-existing-dir/`