copies: prepare changelog for more copies storage mode
We want to store copies information in sidedata, the logic will be quite similar
to the one used for extra, but sightly different (not in extra, no hash impact).
We start with small refactoring to make our work easier and the coming changesets
cleaners.
Differential Revision: https://phab.mercurial-scm.org/D6936
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.