tests/test-issue1089

patchbomb: make `hg email` reusable for other patch sources

Adds two internal options, patches and patchnames, which allow other extensions
to email a given set of patches. The pbranch extension needs this to send its
patches which are diffs between topic branches.

#!/bin/sh

hg init a
cd a
mkdir a
echo a > a/b
hg ci -Am m
hg rm a
hg ci -m m a

mkdir a b
echo a > a/b
hg ci -Am m
hg rm a
cd b
# relative delete
hg ci -m m ../a