tests/test-repair-strip.t

commit: improve the files field of changelog for merges

Currently, the files list of merge commits repeats all the deletions
(either actual deletions, or files that got renamed) that happened
between base and p2 of the merge. If p2 is the main branch, the list
can easily be much bigger than the change being merged.

This results in various problems worth improving:
- changelog is bigger than necessary
- `hg log directory` lists many unrelated merge commits, and `hg log
  -v -r commit` frequently fills multiple screens worth of files
- it possibly slows down adjustlinkrev, by forcing it to read more
  manifests, and that function can certainly be a bottleneck
- the server side of pulls can waste a lot of time simply opening the
  filelogs for pointless files (the constant factors for opening even
  a tiny filelog is apparently pretty bad)

So stop listing such files as described in the code.  Impacted merge
commits and their descendants get a different hash than they would
have without this. This doesn't seem problematic, except for
convert. The previous commit helped with that in the hg->hg case (but
if you do svn->hg twice from scratch, hashes can still change).

The rest of the description is numbers. I don't have much to report,
because recreating the files list of existing repositories is not
easy:
- debugupgradeformat and bundle/unbundle don't recreate the list
- export/import tends to choke quickly applying patches or on
  description that contain diffs,
- merge commits from the convert extension don't have the right files
  list for reasons orthogonal to the current commit
- replaying the merge with hg update/hg merge/hg revert --all/hg
  commit can end up failing in hg revert
- I wasn't sure that using debugsetparents + debugrebuilddirstate
  would really build the right thing

I measured commit time before and after this change, in a case with no
files filtered out, several files filtered out (no difference) and 5k
files filtered out (+1% time).

Recreating the 100 more recent merges in a private repo, the
concatenated uncompressed files lists goes from 1.12MB to
0.52MB. Excluding 3 merges that are not representative, then the size
goes from 570k to 15k.
I converted part of mozilla-central, and observed file list shrinking
quite a bit too, starting at the very first merge, 733641d9feaf, going
from 550 files to 10 files (although they have relatively few merges,
so they probably wouldn't care).

Differential Revision: https://phab.mercurial-scm.org/D6613

#require unix-permissions no-root reporevlogstore

  $ cat > $TESTTMP/dumpjournal.py <<EOF
  > import sys
  > for entry in sys.stdin.read().split('\n'):
  >     if entry:
  >         print(entry.split('\x00')[0])
  > EOF

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=">> $HGRCPATH

  $ teststrip() {
  >   hg -q up -C $1
  >   echo % before update $1, strip $2
  >   hg parents
  >   chmod -$3 $4
  >   hg strip $2 2>&1 | sed 's/\(bundle\).*/\1/' | sed 's/Permission denied.*\.hg\/store\/\(.*\)/Permission denied \.hg\/store\/\1/'
  >   echo % after update $1, strip $2
  >   chmod +$3 $4
  >   hg verify
  >   echo % journal contents
  >   if [ -f .hg/store/journal ]; then
  >       cat .hg/store/journal | "$PYTHON" $TESTTMP/dumpjournal.py
  >   else
  >       echo "(no journal)"
  >   fi
  >   ls .hg/store/journal >/dev/null 2>&1 && hg recover
  >   ls .hg/strip-backup/* >/dev/null 2>&1 && hg unbundle -q .hg/strip-backup/*
  >   rm -rf .hg/strip-backup
  > }

  $ hg init test
  $ cd test
  $ echo a > a
  $ hg -q ci -m "a" -A
  $ echo b > b
  $ hg -q ci -m "b" -A
  $ echo b2 >> b
  $ hg -q ci -m "b2" -A
  $ echo c > c
  $ hg -q ci -m "c" -A
  $ teststrip 0 2 w .hg/store/data/b.i
  % before update 0, strip 2
  changeset:   0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
  saved backup bundle
  transaction abort!
  failed to truncate data/b.i
  rollback failed - please run hg recover
  (failure reason: [Errno 13] Permission denied .hg/store/data/b.i')
  strip failed, backup bundle
  abort: Permission denied .hg/store/data/b.i'
  % after update 0, strip 2
  abandoned transaction found - run hg recover
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
   b@?: rev 1 points to nonexistent changeset 2
   (expected 1)
   b@?: 736c29771fba not in manifests
  warning: orphan data file 'data/c.i'
  checked 2 changesets with 3 changes to 2 files
  2 warnings encountered!
  2 integrity errors encountered!
  % journal contents
  00changelog.i
  00manifest.i
  data/b.i
  data/c.i
  rolling back interrupted transaction
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 2 changesets with 2 changes to 2 files
  $ teststrip 0 2 r .hg/store/data/b.i
  % before update 0, strip 2
  changeset:   0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
  abort: Permission denied .hg/store/data/b.i'
  % after update 0, strip 2
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 4 changes to 3 files
  % journal contents
  (no journal)
  $ teststrip 0 2 w .hg/store/00manifest.i
  % before update 0, strip 2
  changeset:   0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
  saved backup bundle
  transaction abort!
  failed to truncate 00manifest.i
  rollback failed - please run hg recover
  (failure reason: [Errno 13] Permission denied .hg/store/00manifest.i')
  strip failed, backup bundle
  abort: Permission denied .hg/store/00manifest.i'
  % after update 0, strip 2
  abandoned transaction found - run hg recover
  checking changesets
  checking manifests
   manifest@?: rev 2 points to nonexistent changeset 2
   manifest@?: 3362547cdf64 not in changesets
   manifest@?: rev 3 points to nonexistent changeset 3
   manifest@?: 265a85892ecb not in changesets
  crosschecking files in changesets and manifests
   c@3: in manifest but not in changeset
  checking files
   b@?: rev 1 points to nonexistent changeset 2
   (expected 1)
   c@?: rev 0 points to nonexistent changeset 3
  checked 2 changesets with 4 changes to 3 files
  1 warnings encountered!
  7 integrity errors encountered!
  (first damaged changeset appears to be 3)
  % journal contents
  00changelog.i
  00manifest.i
  data/b.i
  data/c.i
  rolling back interrupted transaction
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 2 changesets with 2 changes to 2 files

  $ cd ..