On the pin-externals branch, add a comment.
On the pin-externals branch, add a comment.

* subversion/cmdline/externals_tests.py
  (copy_pin_externals): Explain why exdir_H is expected to be pinned to r1.


git-svn-id: 50c5f5df37af4354ae6e67714fc94b8d09273154@1654535 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion