refactor common behavior between git loader and dir loader

specifically: the batching/transfer parts are largely the same and should go into a loader-common module or something

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Migrated from T89 (view on Phabricator)

added Directory loader Git loader priority:Wishlist labels

changed title from Extract common behavior between swh-loader-git and swh-loader-dir ~> swh-loader-core to refactor common behavior between git loader and dir loader

changed the description

added priority:Low label and removed priority:Wishlist label

(since quite a while, thanks to swh.loader.core)

assigned to @zack

closed

mentioned in issue #117 (closed)