gc: add tests for --cruft and friends
In
5b92477f89 (builtin/gc.c: conditionally avoid pruning objects via
loose, 2022-05-20) gc learned to respect '--cruft' and 'gc.cruftPacks'.
'--cruft' is exercised in t5329-pack-objects-cruft.sh, but in a way that
doesn't check whether a lone gc run generates these cruft packs.
'gc.cruftPacks' is never exercised.
Add some tests to exercise these options to gc in the gc test suite.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>