revlog: avoid large yields in group()
Split large yields so that the downstream consumer (chunkbuffer) will avoid
some pain when reading ahead.
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.