There are all sorts of misconfiguration in the wild. We already rely
on the signature constructor to trim SP. Extend the logic to use
`isspace` to decide whether a character should be trimmed.
Created a copy of tests/resources/testrepo.git that is compatible
with the Clar sandboxing helpers.
Restructured commit test suites to use Clar sandbox helpers.
Now using typed data arrays rather than lots of macros to define test
cases.
