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.

mercurial/repair.py

@@ -167,6 +167,13 b' def strip(ui, repo, nodelist, backup=Tru'
             tr.startgroup()
             cl.strip(striprev, tr)
             mfst.strip(striprev, tr)
+            if 'treemanifest' in repo.requirements: # safe but unnecessary
+                                                    # otherwise
+                for unencoded, encoded, size in repo.store.datafiles():
+                    if (unencoded.startswith('meta/') and
+                        unencoded.endswith('00manifest.i')):
+                        dir = unencoded[5:-12]
+                        repo.dirlog(dir).strip(striprev, tr)
             for fn in files:
                 repo.file(fn).strip(striprev, tr)
             tr.endgroup()

tests/test-treemanifest.t

@@ -309,7 +309,16 b' Stripping and recovering changes should '
   $ hg --config extensions.strip= strip tip
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   saved backup bundle to $TESTTMP/repo-mixed/.hg/strip-backup/51cfd7b1e13b-78a2f3ed-backup.hg (glob)
+  $ hg debugindex --dir dir1
+     rev    offset  length  delta linkrev nodeid       p1           p2
+       0         0     127     -1       4 064927a0648a 000000000000 000000000000
+       1       127     111      0       5 25ecb8cb8618 000000000000 000000000000
   $ hg unbundle -q .hg/strip-backup/*
+  $ hg debugindex --dir dir1
+     rev    offset  length  delta linkrev nodeid       p1           p2
+       0         0     127     -1       4 064927a0648a 000000000000 000000000000
+       1       127     111      0       5 25ecb8cb8618 000000000000 000000000000
+       2       238      55      1       6 5b16163a30c6 25ecb8cb8618 000000000000
   $ hg st --change tip
   M dir1/a