convert: disable current --filemap support
The --filemap support in hg convert doesn't handle merges correctly.
(And after 33015dac5df5 I managed to break it even for simple cases
where we don't want the first revision.)
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://www.selenic.com/mercurial/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.