tests/test-merge-commit.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

Check that renames are correctly saved by a commit after a merge

Test with the merge on 3 having the rename on the local parent

  $ hg init a
  $ cd a

  $ echo line1 > foo
  $ hg add foo
  $ hg ci -m '0: add foo'

  $ echo line2 >> foo
  $ hg ci -m '1: change foo'

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg mv foo bar
  $ rm bar
  $ echo line0 > bar
  $ echo line1 >> bar
  $ hg ci -m '2: mv foo bar; change bar'
  created new head

  $ hg merge 1
  merging bar and foo to bar
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line0
  line1
  line2

  $ hg ci -m '3: merge with local rename'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825

  $ hg debugrename bar
  bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2

  $ hg debugindex foo
     rev linkrev nodeid       p1           p2
       0       0 690b295714ae 000000000000 000000000000
       1       1 9e25c27b8757 690b295714ae 000000000000


Revert the content change from rev 2:

  $ hg up -C 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar
  $ echo line1 > bar
  $ hg ci -m '4: revert content change from rev 2'
  created new head

  $ hg log --template '{rev}:{node|short} {parents}\n'
  4:2263c1be0967 2:0f2ff26688b9 
  3:0555950ead28 2:0f2ff26688b9 1:5cd961e4045d 
  2:0f2ff26688b9 0:2665aaee66e9 
  1:5cd961e4045d 
  0:2665aaee66e9 

This should use bar@rev2 as the ancestor:

  $ hg --debug merge 3
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 0555950ead28
   preserving bar for resolve of bar
  starting 4 threads for background file closing (?)
   bar: versions differ -> m (premerge)
  picked tool ':merge' for bar (binary False symlink False changedelete False)
  merging bar
  my bar@2263c1be0967+ other bar@0555950ead28 ancestor bar@0f2ff26688b9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line1
  line2

  $ hg ci -m '5: merge'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825
       2       4 ff4b45017382 d35118874825 000000000000
       3       5 3701b4893544 ff4b45017382 5345f5ab8abd


Same thing, but with the merge on 3 having the rename
on the remote parent:

  $ cd ..
  $ hg clone -U -r 1 -r 2 a b
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 2 files (+1 heads)
  new changesets 2665aaee66e9:0f2ff26688b9
  $ cd b

  $ hg up -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge 2
  merging foo and bar to bar
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line0
  line1
  line2

  $ hg ci -m '3: merge with remote rename'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825

  $ hg debugrename bar
  bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2

  $ hg debugindex foo
     rev linkrev nodeid       p1           p2
       0       0 690b295714ae 000000000000 000000000000
       1       1 9e25c27b8757 690b295714ae 000000000000


Revert the content change from rev 2:

  $ hg up -C 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar
  $ echo line1 > bar
  $ hg ci -m '4: revert content change from rev 2'
  created new head

  $ hg log --template '{rev}:{node|short} {parents}\n'
  4:2263c1be0967 2:0f2ff26688b9 
  3:3ffa6b9e35f0 1:5cd961e4045d 2:0f2ff26688b9 
  2:0f2ff26688b9 0:2665aaee66e9 
  1:5cd961e4045d 
  0:2665aaee66e9 

This should use bar@rev2 as the ancestor:

  $ hg --debug merge 3
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 3ffa6b9e35f0
   preserving bar for resolve of bar
  starting 4 threads for background file closing (?)
   bar: versions differ -> m (premerge)
  picked tool ':merge' for bar (binary False symlink False changedelete False)
  merging bar
  my bar@2263c1be0967+ other bar@3ffa6b9e35f0 ancestor bar@0f2ff26688b9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line1
  line2

  $ hg ci -m '5: merge'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825
       2       4 ff4b45017382 d35118874825 000000000000
       3       5 3701b4893544 ff4b45017382 5345f5ab8abd

  $ cd ..