copies: show we can read data from the "first" mapping
In practice this make no difference since `t` is a copy of `a`. Having this
change before hand will make the next cleanup changeset clearer.
This is work on the road to using some native code for some performance critical
part of copy tracing.
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.