tests/test-config-case.t

bookmarks: fix head selection for merge with two bookmarked heads

A type mismatch caused the search for the other head to fail. The code is
fragile, and instead it ended up using the 'first' bookmark head, but the
ordering is undefined and it could thus randomly use the wrong bookmarkhead
and fail with:

  $ hg up -q -C e@diverged
  $ hg merge
  abort: merging with a working directory ancestor has no effect

hide outer repo
  $ hg init

  $ echo '[Section]' >> $HGRCPATH
  $ echo 'KeY = Case Sensitive' >> $HGRCPATH
  $ echo 'key = lower case' >> $HGRCPATH

  $ hg showconfig Section
  Section.KeY=Case Sensitive
  Section.key=lower case