tests/test-transaction-rollback-on-revlog-split.t

localrepo: stop doing special dirstate backup at transaction open

Since the dirstate writes are already managed by the transaction, we already do
a backup of the dirstate when necessary (and even trigger one to keep `hg
rollback` happy).

We needs some special code to deal with the initial empty checkout, but it is
not too complicated.

Managing variable filename (as dirstate-v2 uses) at the "journalfile" level, is
complex and fragile (which is consistent with the fact these files are not
journal…). If we no longer do it, our life is significantly simpler.

In some sense, we apply the xkcd-1134¹ solution to our savebackup/restorebackup
problem.

[1] https://xkcd.com/1134/

(the change to test-hardlink are expect as decreasing the number of duplicated
backup drive the hardlink count down)

Test correctness of revlog inline -> non-inline transition
----------------------------------------------------------

Helper extension to intercept renames.

  $ cat > $TESTTMP/intercept_rename.py << EOF
  > import os
  > import sys
  > from mercurial import extensions, util
  > 
  > def extsetup(ui):
  >     def close(orig, *args, **kwargs):
  >         path = util.normpath(args[0]._atomictempfile__name)
  >         if path.endswith(b'/.hg/store/data/file.i'):
  >             os._exit(80)
  >         return orig(*args, **kwargs)
  >     extensions.wrapfunction(util.atomictempfile, 'close', close)
  > EOF

Test offset computation to correctly factor in the index entries themselves.
Also test that the new data size has the correct size if the transaction is aborted
after the index has been replaced.

Test repo has commits a, b, c, D, where D is large (grows the revlog enough that it
transitions to non-inline storage). The clone initially has changes a, b
and will transition to non-inline storage when adding c, D.

If the transaction adding c, D is rolled back, then we don't undo the revlog split,
but truncate the index and the data to remove both c and D.

  $ hg init troffset-computation --config format.revlog-compression=none
  $ cd troffset-computation
  $ printf '%20d' '1' > file
  $ hg commit -Aqma
  $ printf '%1024d' '1' > file
  $ hg commit -Aqmb
  $ printf '%20d' '1' > file
  $ hg commit -Aqmc
  $ dd if=/dev/zero of=file bs=1k count=128 > /dev/null 2>&1
  $ hg commit -AqmD

  $ cd ..

  $ hg clone -r 1 troffset-computation troffset-computation-copy --config format.revlog-compression=none -q
  $ cd troffset-computation-copy

Reference size:

  $ f -s .hg/store/data/file*
  .hg/store/data/file.i: size=1174

  $ cat > .hg/hgrc <<EOF
  > [hooks]
  > pretxnchangegroup = python:$TESTDIR/helper-killhook.py:killme
  > EOF
#if chg
  $ hg pull ../troffset-computation
  pulling from ../troffset-computation
  [255]
#else
  $ hg pull ../troffset-computation
  pulling from ../troffset-computation
  [80]
#endif
  $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file | tail -1
  data/file.i 128

The first file.i entry should match the "Reference size" above.
The first file.d entry is the temporary record during the split,
the second entry after the split happened. The sum of the second file.d
and the second file.i entry should match the first file.i entry.

  $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file
  data/file.i 1174
  data/file.d 0
  data/file.d 1046
  data/file.i 128
  $ hg recover
  rolling back interrupted transaction
  (verify step skipped, run `hg verify` to check your repository content)
  $ f -s .hg/store/data/file*
  .hg/store/data/file.d: size=1046
  .hg/store/data/file.i: size=128
  $ hg tip
  changeset:   1:cfa8d6e60429
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg verify -q
   warning: revlog 'data/file.d' not in fncache!
  1 warnings encountered!
  hint: run "hg debugrebuildfncache" to recover from corrupt fncache
  $ hg debugrebuildfncache --only-data
  adding data/file.d
  1 items added, 0 removed from fncache
  $ hg verify -q
  $ cd ..


Now retry the procedure but intercept the rename of the index and check that
the journal does not contain the new index size. This demonstrates the edge case
where the data file is left as garbage.

  $ hg clone -r 1 troffset-computation troffset-computation-copy2 --config format.revlog-compression=none -q
  $ cd troffset-computation-copy2
  $ cat > .hg/hgrc <<EOF
  > [extensions]
  > intercept_rename = $TESTTMP/intercept_rename.py
  > [hooks]
  > pretxnchangegroup = python:$TESTDIR/helper-killhook.py:killme
  > EOF
#if chg
  $ hg pull ../troffset-computation
  pulling from ../troffset-computation
  [255]
#else
  $ hg pull ../troffset-computation
  pulling from ../troffset-computation
  [80]
#endif
  $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file
  data/file.i 1174
  data/file.d 0
  data/file.d 1046

  $ hg recover
  rolling back interrupted transaction
  (verify step skipped, run `hg verify` to check your repository content)
  $ f -s .hg/store/data/file*
  .hg/store/data/file.d: size=1046
  .hg/store/data/file.i: size=1174
  $ hg tip
  changeset:   1:cfa8d6e60429
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg verify -q
  $ cd ..


Repeat the original test but let hg rollback the transaction.

  $ hg clone -r 1 troffset-computation troffset-computation-copy-rb --config format.revlog-compression=none -q
  $ cd troffset-computation-copy-rb
  $ cat > .hg/hgrc <<EOF
  > [hooks]
  > pretxnchangegroup = false
  > EOF
  $ hg pull ../troffset-computation
  pulling from ../troffset-computation
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  transaction abort!
  rollback completed
  abort: pretxnchangegroup hook exited with status 1
  [40]
  $ f -s .hg/store/data/file*
  .hg/store/data/file.d: size=1046
  .hg/store/data/file.i: size=128
  $ hg tip
  changeset:   1:cfa8d6e60429
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg verify -q
   warning: revlog 'data/file.d' not in fncache!
  1 warnings encountered!
  hint: run "hg debugrebuildfncache" to recover from corrupt fncache
  $ cd ..