There exists multiple implementations of the mercurial loader.
Only one is now the official swh.loader.mercurial.from_disk.HgLoaderFromDisk.

The other implementations helped for backward compat when crafting the new one.
Now that's it's landed and used, those should be cleaned up to avoid a high burden maintenance.

The official one should be renamed to swh.loader.mercurial.loader.HgLoader.

That might be a blocking point for [1] so that may have to come before it.

[1] T3571