tests/test-xdg.t

infinitepush: ensure fileindex bookmarks use '/' separators (issue5840)

After loading up with status messages, I noticed that the subsequent matcher was
rejecting 'scratch\mybranch' on Windows.  No bookmarks were reported back, and
the tests subsequently failed.  I did a search for 'match', and nothing else
looks like it needs to be fixed up, but someone who understands this code should
also take a look.

I also tried setting `infinitepush.branchpattern=re:scratch\\.*` in
library-infinitepush.sh without this change, but that didn't work.  Still,
should we ban '\' in these bookmarks to avoid confusion?  I thought I saw code
that sandwiches a pattern between 're:^' and '.*', so perhaps regex characters
will need special care?

I also noticed comments in externalbundlestore.{read,write} that it won't work
on Windows because of opening an open file.  But I don't see a test failure, so
this may lack test coverage.

#if no-windows no-osx

  $ mkdir -p xdgconf/hg
  $ echo '[ui]' > xdgconf/hg/hgrc
  $ echo 'username = foobar' >> xdgconf/hg/hgrc
  $ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
  $ unset HGRCPATH
  $ hg config ui.username 2>/dev/null
  foobar

#endif