tests/test-strip-cross.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

test stripping of filelogs where the linkrev doesn't always increase

  $ echo '[extensions]' >> $HGRCPATH
  $ echo 'strip =' >> $HGRCPATH
  $ hg init orig
  $ cd orig
  $ commit()
  > {
  >     hg up -qC null
  >     count=1
  >     for i in "$@"; do
  >         for f in $i; do
  >             echo $count > $f
  >         done
  >         count=`expr $count + 1`
  >     done
  >     hg commit -qAm "$*"
  > }

2 1 0 2 0 1 2

  $ commit '201 210'
  $ commit '102 120' '210'
  $ commit '021'
  $ commit '201' '021 120'
  $ commit '012 021' '102 201' '120 210'
  $ commit 'manifest-file'
  $ commit '102 120' '012 210' '021 201'
  $ commit '201 210' '021 120' '012 102'
  $ HGUSER=another-user; export HGUSER
  $ commit 'manifest-file'
  $ commit '012' 'manifest-file'
  $ cd ..
  $ hg clone -q -U -r -1 -r -2 -r -3 -r -4 -r -6 orig crossed
  $ cd crossed
  $ hg debugindex --manifest
     rev linkrev nodeid       p1           p2
       0       0 6f105cbb914d 000000000000 000000000000
       1       3 1b55917b3699 000000000000 000000000000
       2       1 8f3d04e263e5 000000000000 000000000000
       3       2 f0ef8726ac4f 000000000000 000000000000
       4       4 0b76e38b4070 000000000000 000000000000

  $ for i in 012 021 102 120 201 210 manifest-file; do
  >     echo $i
  >     hg debugindex $i
  >     echo
  > done
  012
     rev linkrev nodeid       p1           p2
       0       0 b8e02f643373 000000000000 000000000000
       1       1 5d9299349fc0 000000000000 000000000000
       2       2 2661d26c6496 000000000000 000000000000
  
  021
     rev linkrev nodeid       p1           p2
       0       0 b8e02f643373 000000000000 000000000000
       1       2 5d9299349fc0 000000000000 000000000000
       2       1 2661d26c6496 000000000000 000000000000
  
  102
     rev linkrev nodeid       p1           p2
       0       1 b8e02f643373 000000000000 000000000000
       1       0 5d9299349fc0 000000000000 000000000000
       2       2 2661d26c6496 000000000000 000000000000
  
  120
     rev linkrev nodeid       p1           p2
       0       1 b8e02f643373 000000000000 000000000000
       1       2 5d9299349fc0 000000000000 000000000000
       2       0 2661d26c6496 000000000000 000000000000
  
  201
     rev linkrev nodeid       p1           p2
       0       2 b8e02f643373 000000000000 000000000000
       1       0 5d9299349fc0 000000000000 000000000000
       2       1 2661d26c6496 000000000000 000000000000
  
  210
     rev linkrev nodeid       p1           p2
       0       2 b8e02f643373 000000000000 000000000000
       1       1 5d9299349fc0 000000000000 000000000000
       2       0 2661d26c6496 000000000000 000000000000
  
  manifest-file
     rev linkrev nodeid       p1           p2
       0       3 b8e02f643373 000000000000 000000000000
       1       4 5d9299349fc0 000000000000 000000000000
  
  $ cd ..
  $ for i in 0 1 2 3 4; do
  >     hg clone -q -U --pull crossed $i
  >     echo "% Trying to strip revision $i"
  >     hg --cwd $i strip $i
  >     echo "% Verifying"
  >     hg --cwd $i verify
  >     echo
  > done
  % Trying to strip revision 0
  saved backup bundle to $TESTTMP/0/.hg/strip-backup/*-backup.hg (glob)
  % Verifying
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 15 changes to 7 files
  
  % Trying to strip revision 1
  saved backup bundle to $TESTTMP/1/.hg/strip-backup/*-backup.hg (glob)
  % Verifying
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 14 changes to 7 files
  
  % Trying to strip revision 2
  saved backup bundle to $TESTTMP/2/.hg/strip-backup/*-backup.hg (glob)
  % Verifying
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 14 changes to 7 files
  
  % Trying to strip revision 3
  saved backup bundle to $TESTTMP/3/.hg/strip-backup/*-backup.hg (glob)
  % Verifying
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 19 changes to 7 files
  
  % Trying to strip revision 4
  saved backup bundle to $TESTTMP/4/.hg/strip-backup/*-backup.hg (glob)
  % Verifying
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 4 changesets with 19 changes to 7 files