treemanifests: actually strip directory manifests Stripping has only partly worked since 7cbb3a01fa38 (repair: use cg3 for treemanifests, 2016-01-19): the bundle seems to have been created correctly, but revlog entries in subdirectory revlogs were not stripped. This meant that e.g. "hg verify" would fail after stripping in a tree manifest repo. To find the revisions to strip, we simply iterate over all directories in the repo (included in store.datafiles()). This is inefficient for stripping few commits, but efficient for stripping many commits. To optimize for stripping few commits, we could instead walk the tree from the root and find modified subdirectories, just like we do in the changegroup code. I'm leaving that for another day.