tests/test-default-push.t

branchmap: simplify _branchtags using a new _cacheabletip method

The current _branchtags method is a remnant of an older, much larger function.
Its only remaining role is to help MQ to alter the version of branchcache we
store on disk. As MQ mutates the repository it ensures persistent cache does not
contain anything it is likely to alter.

This changeset makes explicit the stable vs volatile part of repository and
reduces the MQ specific code to the computation of this limit. The main
_branchtags code now handles this possible limit in all cases.

This will help to extract the branchmap logic from the repository.

The new code of _branchtags is a bit duplicated, but as I expect major
refactoring of this section I'm not keen to setup factorisation function here.

  $ hg init a

  $ echo a > a/a
  $ hg --cwd a ci -Ama
  adding a

  $ hg clone a c
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

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

  $ echo b >> b/a
  $ hg --cwd b ci -mb

Push should push to 'default' when 'default-push' not set:

  $ hg --cwd b push
  pushing to $TESTTMP/a (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Push should push to 'default-push' when set:

  $ echo 'default-push = ../c' >> b/.hg/hgrc
  $ hg --cwd b push
  pushing to $TESTTMP/c (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files