archive: autodetect archive type by extension (
issue2058)
tests: use external coverage, mandate newer version
This removes the option for including the stdlib in coverage reports.
rebase: improve help text
- add a paragraph about default dest/source changesets
- option help: say "changeset" not "revision"
- option help: explain -b/--base better
- clarify that -a/--abort and -c/--continue are different from the
other options