tests/test-remotefilelog-linknodes.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 no-windows

# Tests for the complicated linknode logic in remotefilelog.py::ancestormap()

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > serverexpiration=-1
  > EOF
  $ echo x > x
  $ hg commit -qAm x
  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

# Rebase produces correct log -f linknodes

  $ cd shallow
  $ echo y > y
  $ hg commit -qAm y
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo x >> x
  $ hg commit -qAm xx
  $ hg log -f x --template "{node|short}\n"
  0632994590a8
  b292c1e3311f

  $ hg rebase -d 1
  rebasing 2:0632994590a8 "xx" (tip)
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/0632994590a8-0bc786d8-rebase.hg (glob)
  $ hg log -f x --template "{node|short}\n"
  81deab2073bc
  b292c1e3311f

# Rebase back, log -f still works

  $ hg rebase -d 0 -r 2
  rebasing 2:81deab2073bc "xx" (tip)
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/81deab2073bc-80cb4fda-rebase.hg (glob)
  $ hg log -f x --template "{node|short}\n"
  b3fca10fb42d
  b292c1e3311f

  $ hg rebase -d 1 -r 2
  rebasing 2:b3fca10fb42d "xx" (tip)
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/b3fca10fb42d-da73a0c7-rebase.hg (glob)

  $ cd ..

# Reset repos
  $ clearcache

  $ rm -rf master
  $ rm -rf shallow
  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > serverexpiration=-1
  > EOF
  $ echo x > x
  $ hg commit -qAm x
  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

# Rebase stack onto landed commit

  $ cd master
  $ echo x >> x
  $ hg commit -Aqm xx

  $ cd ../shallow
  $ echo x >> x
  $ hg commit -Aqm xx2
  $ echo y >> x
  $ hg commit -Aqm xxy

  $ hg pull -q
  $ hg rebase -d tip
  rebasing 1:4549721d828f "xx2"
  note: not rebasing 1:4549721d828f "xx2", its destination already has all its changes
  rebasing 2:5ef6d97e851c "xxy"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/4549721d828f-b084e33c-rebase.hg (glob)
  $ hg log -f x --template '{node|short}\n'
  4ae8e31c85ef
  0632994590a8
  b292c1e3311f

  $ cd ..

# system cache has invalid linknode, but .hg/store/data has valid

  $ cd shallow
  $ hg strip -r 1 -q
  $ rm -rf .hg/store/data/*
  $ echo x >> x
  $ hg commit -Aqm xx_local
  $ hg log -f x --template '{rev}:{node|short}\n'
  1:21847713771d
  0:b292c1e3311f

  $ cd ..
  $ rm -rf shallow

/* Local linknode is invalid; remote linknode is valid (formerly slow case) */

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over * (glob)
  $ cd shallow
  $ echo x >> x
  $ hg commit -Aqm xx2
  $ cd ../master
  $ echo y >> y
  $ hg commit -Aqm yy2
  $ echo x >> x
  $ hg commit -Aqm xx2-fake-rebased
  $ echo y >> y
  $ hg commit -Aqm yy3
  $ cd ../shallow
  $ hg pull --config remotefilelog.debug=True
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 0 changes to 0 files (+1 heads)
  new changesets 01979f9404f8:7200df4e0aca
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg update tip -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ echo x > x
  $ hg commit -qAm xx3

# At this point, the linknode points to c1254e70bad1 instead of 32e6611f6149
  $ hg log -G -T '{node|short} {desc} {phase} {files}\n'
  @  a5957b6bf0bd xx3 draft x
  |
  o  7200df4e0aca yy3 public y
  |
  o  32e6611f6149 xx2-fake-rebased public x
  |
  o  01979f9404f8 yy2 public y
  |
  | o  c1254e70bad1 xx2 draft x
  |/
  o  0632994590a8 xx public x
  |
  o  b292c1e3311f x public x
  
# Check the contents of the local blob for incorrect linknode
  $ hg debugremotefilelog .hg/store/data/11f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216
  size: 6 bytes
  path: .hg/store/data/11f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216 
  key: d4a3ed9310e5 
  
          node =>           p1            p2      linknode     copyfrom
  d4a3ed9310e5 => aee31534993a  000000000000  c1254e70bad1  
  aee31534993a => 1406e7411862  000000000000  0632994590a8  
  1406e7411862 => 000000000000  000000000000  b292c1e3311f  

# Verify that we do a fetch on the first log (remote blob fetch for linkrev fix)
  $ hg log -f x -T '{node|short} {desc} {phase} {files}\n'
  a5957b6bf0bd xx3 draft x
  32e6611f6149 xx2-fake-rebased public x
  0632994590a8 xx public x
  b292c1e3311f x public x
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

# But not after that
  $ hg log -f x -T '{node|short} {desc} {phase} {files}\n'
  a5957b6bf0bd xx3 draft x
  32e6611f6149 xx2-fake-rebased public x
  0632994590a8 xx public x
  b292c1e3311f x public x

# Check the contents of the remote blob for correct linknode
  $ hg debugremotefilelog $CACHEDIR/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216
  size: 6 bytes
  path: $TESTTMP/hgcache/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216 
  key: d4a3ed9310e5 
  
          node =>           p1            p2      linknode     copyfrom
  d4a3ed9310e5 => aee31534993a  000000000000  32e6611f6149  
  aee31534993a => 1406e7411862  000000000000  0632994590a8  
  1406e7411862 => 000000000000  000000000000  b292c1e3311f