contrib/plan9/mkfile

match: introduce boolean prefix() method

tl;dr: This is another step towards a (previously unstated) goal of
eliminating match.files() in conditions.

There are four types of matchers:

 * always: Matches everything, checked with always(), files() is empty

 * exact: Matches exact set of files, checked with isexact(), files()
   contains the files to match

 * patterns: Matches more complex patterns, checked with anypats(),
   files() contains roots of the matched patterns

 * prefix: Matches simple 'path:' patterns as prefixes ('foo' matches
   both 'foo' and 'foo/bar'), no single method to check, files()
   contains the prefixes to match

For completeness, it would be nice to have a method for checking for
the "prefix" type of matcher as well, so let's add that, making it
return True simply when none of the others do.

The larger goal here is to eliminate uses of match.files() in
conditions (i.e. bool(match.files())). The reason for this is that
there are scenarios when you would like to create a "prefix" matcher
that happens to match no files. One example is for 'hg files -I foo
bar'. The narrowmatcher also restricts the set of files given and it
would not surprise me if have bugs caused by that already. Note that
'if m.files() and not m.anypats()' and similar is sometimes used to
catch the "exact" and "prefix" cases above.

APE=/sys/src/ape
<$APE/config

PYTHON=python
PYTHONBIN=/rc/bin
SH=ape/psh

PURE=--pure
ROOT=../..

# This is slightly underhanded; Plan 9 does not support GNU gettext nor
# does it support dynamically loaded extension modules. We work around
# this by calling build_py and build_scripts directly; this avoids
# additional platform hacks in setup.py.
build:VQ:
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE build_py build_scripts'
	}

clean:VQ:
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE clean --all'
	}

install:VQ:	build
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE install \
			--install-scripts $PYTHONBIN \
			--skip-build \
			--force'
	}
	mkdir -p /lib/mercurial/hgrc.d
	dircp hgrc.d /lib/mercurial/hgrc.d/
	cp 9diff /rc/bin/