patch: deprecate ui.patch / external patcher feature
Why?
- Mercurial internal patcher works correctly for regular patches and git
patches, is much faster at least on Windows and is more extensible.
- In theory, the external patcher can be used to handle exotic patch formats. I
do not know any and have not heard about any such use in years.
- Most patch programs cannot handle git format patches, which makes the API
caller to decide either to ignore ui.patch by calling patch.internalpatch()
directly, or take the risk of random failures with valid inputs.
- One thing a patch program could do Mercurial patcher cannot is applying with
--reverse. Apparently several shelve like extensions try to use that,
including passing the "reverse" option to Mercurial patcher, which has been
removed mid-2009. I never heard anybody complain about that, and would prefer
reimplementing it anyway.
And from the technical perspective:
- The external patcher makes everything harder to maintain and implement. EOL
normalization is not implemented, and I would bet file renames, if supported
by the patcher, are not correctly recorded in the dirstate.
- No tests.
How?
- Remove related documentation
- Clearly mark patch.externalpatch() as private
- Remove the debuginstall check. This deprecation request was actually
triggered by this last point. debuginstall is the only piece of code patching
without a repository. When migrating to an integrated patch() + updatedir()
call, this was really a showstopper, all workarounds were either ugly or
uselessly complicated to implement. If we do not support external patcher
anymore, the debuginstall check is not useful anymore.
- Remove patch.externalpatch() after 1.9 release.
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.