run-tests: remove files that we potentially create outside of $TMPDIR

run-tests: remove code that creates a dummy 'diffstat' This was introduced in fb1d7a42663c for an old test that is no longer the same.

template: change extras to use showlist rather than manual templ call. This enables start_extras and end_extras in template maps.

help: adding example 'extras' printing to 'hg help templates'

help: document about {extras} template keyword This adds text about the "extras" template keyword, similar to that proposed by Yuya Nishihara previously.

check-code: document last ignore regexp For easier remembering to delete when it is not needed anymore.