* Two new functions for getting a list of files and their timestamps
in the repo, and diffing that information to get a list of changed
files: pmb.helpers.repo.files() and pmb.helpers.repo.diff().
(I've put it in the helpers folder, because it is not specific to
one chroot, but to all chroots at once.)
* pmbootstrap challenge (new command introduced a few commits back to
verify, that the contents of an APK file are deterministic) uses
these functions to a) support subpackages and b) optionally
output a list of changed files (this gets used in the pmbuilder
script, which lives outside of this repository).
This commit is progress for #64 again.
Oliver Smith