When fetching objects into a lazily cloned repository, .promisor
files are created with information meant to help debugging. "git
repack" has been taught to carry this information forward to
packfiles that are newly created.
* lp/repack-propagate-promisor-debugging-info:
SQUASH???
t7703: test for promisor file content after geometric repack
t7700: test for promisor file content after repack
repack-promisor: preserve content of promisor files after repack
pack-write: add helper to fill promisor file after repack
pack-write: add explanation to promisor file content