view tests/test-merge-revert2.t @ 42377:0546ead39a7e stable

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

  $ hg init

  $ echo "added file1" > file1
  $ echo "another line of text" >> file1
  $ echo "added file2" > file2
  $ hg add file1 file2
  $ hg commit -m "added file1 and file2"

  $ echo "changed file1" >> file1
  $ hg commit -m "changed file1"

  $ hg -q log
  1:dfab7f3c2efb
  0:c3fa057dd86f
  $ hg id
  dfab7f3c2efb tip

  $ hg update -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  c3fa057dd86f

  $ echo "changed file1" >> file1
  $ hg id
  c3fa057dd86f+

  $ hg revert --no-backup --all
  reverting file1
  $ hg diff
  $ hg status
  $ hg id
  c3fa057dd86f

  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg diff
  $ hg status
  $ hg id
  dfab7f3c2efb tip

  $ hg update -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo "changed file1 different" >> file1

  $ hg update
  merging file1
  warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

  $ hg diff --nodates
  diff -r dfab7f3c2efb file1
  --- a/file1
  +++ b/file1
  @@ -1,3 +1,7 @@
   added file1
   another line of text
  +<<<<<<< working copy: c3fa057dd86f - test: added file1 and file2
  +changed file1 different
  +=======
   changed file1
  +>>>>>>> destination:  dfab7f3c2efb - test: changed file1

  $ hg status
  M file1
  ? file1.orig
  $ hg id
  dfab7f3c2efb+ tip

  $ hg revert --no-backup --all
  reverting file1
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  dfab7f3c2efb tip

  $ hg revert -r tip --no-backup --all
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  dfab7f3c2efb tip

  $ hg update -C
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg diff
  $ hg status
  ? file1.orig
  $ hg id
  dfab7f3c2efb tip