tests/test-revlog-group-emptyiter.t

context: make warning message for hidden revision extensible

Extensions might want to create new filternames and change what revisions
are considered hidden or shown. This is the case for inhibit that enables
direct access to hidden hashes with the visible-directaccess-nowarn filtername.
By using startswith instead of a direct comparison with 'visible' we
allow extensions to do that and not work directly on the 'visible' filtername
used by core.

Issue1678: IndexError when pushing

setting up base repo
  $ hg init a
  $ cd a
  $ touch a
  $ hg ci -Am a
  adding a
  $ cd ..

cloning base repo
  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd b

setting up cset to push
  $ hg up null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ touch a
different msg so we get a clog new entry
  $ hg ci -Am b
  adding a
  created new head

pushing
  $ hg push -f ../a
  pushing to ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)

  $ cd ..