tests/test-check-pyflakes.t

hg: establish function for performing post-share actions

As part of writing an extension that wished to share an arbitrary piece
of data among shared repos, I had to reimplement a significant part of
hg.share in order to obtain localrepository instances for the source
and destination.

This patch establishes a function in hg.py that will be called after a
share is performed. It is passed localrepository instances so extensions
can easily perform additional actions at share time. We move hgrc and
shared file writing there because this function is a logical place for
it.

A side effect of the refactor is writing of the shared file now occurs
before updating. This seems more appropriate and shouldn't have any
impact on real world behavior.

#require test-repo pyflakes

  $ cd "`dirname "$TESTDIR"`"

run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)

  $ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
  > | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"
  tests/filterpyflakes.py:61: undefined name 'undefinedname'