clonebundles: move a bundle of clone bundle related code to a new module In the process on general clone bundle automatically, we need to make some function available more widely. This is a good opportunity to extract a significant amount of code from `mercurial.exchange` into a new `mercurial.bundlecaches`. This make `mercurial.exchange` move under the 3K line range (hooray…). The module is called `bundlecaches` because I expect it to be eventually useful for more than just clone bundle (like pull bunbles). Differential Revision: https://phab.mercurial-scm.org/D9208

Mercurial
=========

Mercurial is a fast, easy to use, distributed revision control tool
for software developers.

Basic install::

 $ make            # see install targets
 $ make install    # do a system-wide install
 $ hg debuginstall # sanity-check setup
 $ hg              # see help

Running without installing::

 $ make local      # build for inplace usage
 $ ./hg --version  # should show the latest version

See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.