Merge branch 'sr/vcs-helper'

Merge branch 'sr/vcs-helper'

* sr/vcs-helper:
  tests: handle NO_PYTHON setting
  builtin-push: don't access freed transport->url
  Add Python support library for remote helpers
  Basic build infrastructure for Python scripts
  Allow helpers to report in "list" command that the ref is unchanged
  Fix various memory leaks in transport-helper.c
  Allow helper to map private ref names into normal names
  Add support for "import" helper command
  Allow specifying the remote helper in the url
  Add a config option for remotes to specify a foreign vcs
  Allow fetch to modify refs
  Use a function to determine whether a remote is valid
  Allow programs to not depend on remotes having urls
  Fix memory leak in helper method for disconnect

Conflicts:
	Documentation/git-remote-helpers.txt
	Makefile
	builtin-ls-remote.c
	builtin-push.c
	transport-helper.c