revert: add a way for external extensions to prefetch file data
This allow extensions that mess with the storage layer (remotefilelog,
largefile) to prefetch any data that will be accessed during the revert
operation.
We are currently fetching more data than theoretically required because the
backup code is a bit stupid. Future patches will improve that.
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.