linting, testing; coverage reported 28.1%

linting, testing; coverage reported 28.1%

monkeypatch to fix kcov invocation on posix shell
(add dedicated target for pure /bin/sh testing)

remove old redundant exit 0 in test
add force push/SIGINT tests
fix silently passing (actually failing!) test

force push reword [TODO: restore require-explicit-force-push]
manifest versioning to help verify compatible & authenticity
show signer version; inject version to test
require --force to init or overwrite manifest

split up large repacking test
add separate test for repack with large objects

add method to clean unencrypted files off remote
prevent privacy leaks of previously unencrypted blob

privacy test
more safety/privacy checks and clean command/check early in execution
don't publish participants in new test
remove useless debug log statement

tidy default fetch; small fix to init