smartset: extract spanset factory to make it constructed without a repo
This renames the spanset class to _spanset, and moves its __init__ to new
spanset() function. spanset() is now a factory function.
This allows us to construct a spanset without keeping a repo instance.
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.