tests/test-mq-qgoto.out

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.

adding a
Now at: a.patch
applying b.patch
applying c.patch
Now at: c.patch
Now at: b.patch