doc/README

delta: exclude base candidate much smaller than the target

If a revision's full text is that much bigger than a base candidate full text,
we no longer consider that candidate.

This solves a pathological case we encountered on a very specify repository.
It contains a long series of changesets with a very small manifest (one file)
co-existing with others changesets using a very large manifest.

Without this filtering, we ended up considering a large number of tiny full
snapshots as a potential base. It resulted in very large delta (the size of
the full text) and mercurial spending 99% of its time compressing these
deltas.

The timing of a commit moved from about 400s to about 10s (still slow, but not
ridiculously slow).

Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:

  http://docutils.sourceforge.net/rst.html

It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:

  http://docutils.sourceforge.net/

Use the Makefile in this directory to generate the man and HTML pages.