manifest: avoid corruption by dropping removed files with pure (issue5801) Previously, removed files would simply be marked by overwriting the first byte with NUL and dropping their entry in `self.position`. But no effort was made to ignore them when compacting the dictionary into text form. This allowed them to slip into the manifest revision, since the code seems to be trying to minimize the string operations by copying as large a chunk as possible. As part of this, compact() walks the existing text based on entries in the `positions` list, and consumed everything up to the next position entry. This typically resulted in a ValueError complaining about unsorted manifest entries. Sometimes it seems that files do get dropped in large repos- it seems to correspond to there being a new entry that would take the same slot. A much more trivial problem is that if the only changes were removals, `_compact()` didn't even run because `__delitem__` doesn't add anything to `self.extradata`. Now there's an explicit variable to flag this, both to allow `_compact()` to run, and to avoid searching the manifest in cases where there are no removals. In practice, this behavior was mostly obscured by the check in fastdelta() which takes a different path that explicitly drops removed files if there are fewer than 1000 changes. However, timeless has a repo where after rebasing tens of commits, a totally different path[1] is taken that bypasses the change count check and hits this problem. [1] https://www.mercurial-scm.org/repo/hg/file/2338bdea4474/mercurial/manifest.py#l1511

tests: demonstrate broken manifest generation with the pure module This will be fixed next. But I don't fully understand how 'b.txt' is actually removed properly in the second test, given what's broken. Also, I'm not sure why 'bb.txt' is flagged as not being in the manifest, when it clearly appears to be.

bookmark: also make bookmark cache depends of the changelog Since the changelog is also used during the parsing of bookmark data, it should be listed as a file cache dependency. This fix the race condition we just introduced a test for. This is a simple fix that might lead bookmark data to be invalidated more often than necessary. We could have more complicated code to deal with this race in a more "optimal" way. I feel it would be unsuitable for stable. In addition, the performance impact of this is probably minimal and I don't foresee the more advanced fix to actually be necessary.