tests/test-rebase-conflicts.t

revlog: change generaldelta delta parent heuristic

The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text,
use it, otherwise use prev". This was problematic when a repo contained multiple
branches that were very different. If commits to branch A were pushed, and the
last full text was branch B, it would generate a fulltext. Then if branch B was
pushed, it would generate another fulltext. The problem is that the last
fulltext (and delta'ing against `prev` in general) has no correlation with the
contents of the incoming revision, and therefore will always have degenerate
cases.

According to the blame, that algorithm was chosen to minimize the chain length.
Since there is already code that protects against that (the delta-vs-fulltext
code), and since it has been improved since the original generaldelta algorithm
went in (2011), I believe the chain length criteria will still be preserved.

The new algorithm always diffs against p1 (or p2 if it's closer), unless the
resulting delta will fail the delta-vs-fulltext check, in which case we delta
against prev.

Some before and after stats on manifest.d size.

internal large repo
old heuristic - 2.0 GB
new heuristic - 1.2 GB

mozilla-central
old heuristic - 242 MB
new heuristic - 261 MB

The regression in mozilla central is due to the new heuristic choosing p2r as
the delta when it's closer to the tip. Switching the algorithm to always prefer
p1r brings the size back down (242 MB). This is result of the way in which
mozilla does merges and pushes, and the result could easily swing the other
direction in other repos (depending on if they merge X into Y or Y into X), but
will never be as degenerate as before.

I future patch will address the regression by introducing an optional, even more
aggressive delta heuristic which will knock the mozilla manifest size down
dramatically.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog = log -G --template "{rev}:{phase} '{desc}' {branches} {bookmarks}\n"
  > EOF

  $ hg init a
  $ cd a
  $ echo c1 >common
  $ hg add common
  $ hg ci -m C1

  $ echo c2 >>common
  $ hg ci -m C2

  $ echo c3 >>common
  $ hg ci -m C3

  $ hg up -q -C 1

  $ echo l1 >>extra
  $ hg add extra
  $ hg ci -m L1
  created new head

  $ sed -e 's/c2/l2/' common > common.new
  $ mv common.new common
  $ hg ci -m L2

  $ echo l3 >> extra2
  $ hg add extra2
  $ hg ci -m L3
  $ hg bookmark mybook

  $ hg phase --force --secret 4

  $ hg tglog
  @  5:secret 'L3'  mybook
  |
  o  4:secret 'L2'
  |
  o  3:draft 'L1'
  |
  | o  2:draft 'C3'
  |/
  o  1:draft 'C2'
  |
  o  0:draft 'C1'
  
Try to call --continue:

  $ hg rebase --continue
  abort: no rebase in progress
  [255]

Conflicting rebase:

  $ hg rebase -s 3 -d 2
  rebasing 3:3163e20567cc "L1"
  rebasing 4:46f0b057b5c0 "L2"
  merging common
  warning: conflicts during merge.
  merging common incomplete! (edit conflicts, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

Try to continue without solving the conflict:

  $ hg rebase --continue
  already rebased 3:3163e20567cc "L1" as 3e046f2ecedb
  rebasing 4:46f0b057b5c0 "L2"
  abort: unresolved merge conflicts (see "hg help resolve")
  [255]

Conclude rebase:

  $ echo 'resolved merge' >common
  $ hg resolve -m common
  (no more unresolved files)
  $ hg rebase --continue
  already rebased 3:3163e20567cc "L1" as 3e046f2ecedb
  rebasing 4:46f0b057b5c0 "L2"
  rebasing 5:8029388f38dc "L3" (mybook)
  saved backup bundle to $TESTTMP/a/.hg/strip-backup/3163e20567cc-5ca4656e-backup.hg (glob)

  $ hg tglog
  @  5:secret 'L3'  mybook
  |
  o  4:secret 'L2'
  |
  o  3:draft 'L1'
  |
  o  2:draft 'C3'
  |
  o  1:draft 'C2'
  |
  o  0:draft 'C1'
  
Check correctness:

  $ hg cat -r 0 common
  c1

  $ hg cat -r 1 common
  c1
  c2

  $ hg cat -r 2 common
  c1
  c2
  c3

  $ hg cat -r 3 common
  c1
  c2
  c3

  $ hg cat -r 4 common
  resolved merge

  $ hg cat -r 5 common
  resolved merge

Bookmark stays active after --continue
  $ hg bookmarks
   * mybook                    5:d67b21408fc0

  $ cd ..

Check that the right ancestors is used while rebasing a merge (issue4041)

  $ hg clone "$TESTDIR/bundles/issue4041.hg" issue4041
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 11 changesets with 8 changes to 3 files (+1 heads)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd issue4041
  $ hg log -G
  o    changeset:   10:2f2496ddf49d
  |\   branch:      f1
  | |  tag:         tip
  | |  parent:      7:4c9fbe56a16f
  | |  parent:      9:e31216eec445
  | |  user:        szhang
  | |  date:        Thu Sep 05 12:59:39 2013 -0400
  | |  summary:     merge
  | |
  | o  changeset:   9:e31216eec445
  | |  branch:      f1
  | |  user:        szhang
  | |  date:        Thu Sep 05 12:59:10 2013 -0400
  | |  summary:     more changes to f1
  | |
  | o    changeset:   8:8e4e2c1a07ae
  | |\   branch:      f1
  | | |  parent:      2:4bc80088dc6b
  | | |  parent:      6:400110238667
  | | |  user:        szhang
  | | |  date:        Thu Sep 05 12:57:59 2013 -0400
  | | |  summary:     bad merge
  | | |
  o | |  changeset:   7:4c9fbe56a16f
  |/ /   branch:      f1
  | |    parent:      2:4bc80088dc6b
  | |    user:        szhang
  | |    date:        Thu Sep 05 12:54:00 2013 -0400
  | |    summary:     changed f1
  | |
  | o  changeset:   6:400110238667
  | |  branch:      f2
  | |  parent:      4:12e8ec6bb010
  | |  user:        szhang
  | |  date:        Tue Sep 03 13:58:02 2013 -0400
  | |  summary:     changed f2 on f2
  | |
  | | @  changeset:   5:d79e2059b5c0
  | | |  parent:      3:8a951942e016
  | | |  user:        szhang
  | | |  date:        Tue Sep 03 13:57:39 2013 -0400
  | | |  summary:     changed f2 on default
  | | |
  | o |  changeset:   4:12e8ec6bb010
  | |/   branch:      f2
  | |    user:        szhang
  | |    date:        Tue Sep 03 13:57:18 2013 -0400
  | |    summary:     created f2 branch
  | |
  | o  changeset:   3:8a951942e016
  | |  parent:      0:24797d4f68de
  | |  user:        szhang
  | |  date:        Tue Sep 03 13:57:11 2013 -0400
  | |  summary:     added f2.txt
  | |
  o |  changeset:   2:4bc80088dc6b
  | |  branch:      f1
  | |  user:        szhang
  | |  date:        Tue Sep 03 13:56:20 2013 -0400
  | |  summary:     added f1.txt
  | |
  o |  changeset:   1:ef53c9e6b608
  |/   branch:      f1
  |    user:        szhang
  |    date:        Tue Sep 03 13:55:26 2013 -0400
  |    summary:     created f1 branch
  |
  o  changeset:   0:24797d4f68de
     user:        szhang
     date:        Tue Sep 03 13:55:08 2013 -0400
     summary:     added default.txt
  
  $ hg rebase -s9 -d2 --debug # use debug to really check merge base used
  rebase onto 2 starting from e31216eec445
  ignoring null merge rebase of 3
  ignoring null merge rebase of 4
  ignoring null merge rebase of 6
  ignoring null merge rebase of 8
  rebasing 9:e31216eec445 "more changes to f1"
   future parents are 2 and -1
  rebase status stored
   update to 2:4bc80088dc6b
  resolving manifests
   branchmerge: False, force: True, partial: False
   ancestor: d79e2059b5c0+, local: d79e2059b5c0+, remote: 4bc80088dc6b
   f2.txt: other deleted -> r
  removing f2.txt
   f1.txt: remote created -> g
  getting f1.txt
   merge against 9:e31216eec445
     detach base 8:8e4e2c1a07ae
    searching for copies back to rev 3
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: 8e4e2c1a07ae, local: 4bc80088dc6b+, remote: e31216eec445
   f1.txt: remote is newer -> g
  getting f1.txt
  committing files:
  f1.txt
  committing manifest
  committing changelog
  rebased as 19c888675e13
  rebasing 10:2f2496ddf49d "merge" (tip)
   future parents are 11 and 7
  rebase status stored
   already in target
   merge against 10:2f2496ddf49d
     detach base 9:e31216eec445
    searching for copies back to rev 3
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: e31216eec445, local: 19c888675e13+, remote: 2f2496ddf49d
   f1.txt: remote is newer -> g
  getting f1.txt
  committing files:
  f1.txt
  committing manifest
  committing changelog
  rebased as 2a7f09cac94c
  rebase merging completed
  update back to initial working directory parent
  resolving manifests
   branchmerge: False, force: False, partial: False
   ancestor: 2a7f09cac94c, local: 2a7f09cac94c+, remote: d79e2059b5c0
   f1.txt: other deleted -> r
  removing f1.txt
   f2.txt: remote created -> g
  getting f2.txt
  2 changesets found
  list of changesets:
  e31216eec445e44352c5f01588856059466a24c9
  2f2496ddf49d69b5ef23ad8cf9fb2e0e4faf0ac2
  saved backup bundle to $TESTTMP/issue4041/.hg/strip-backup/e31216eec445-15f7a814-backup.hg (glob)
  3 changesets found
  list of changesets:
  4c9fbe56a16f30c0d5dcc40ec1a97bbe3325209c
  19c888675e133ab5dff84516926a65672eaf04d9
  2a7f09cac94c7f4b73ebd5cd1a62d3b2e8e336bf
  adding branch
  adding changesets
  add changeset 4c9fbe56a16f
  add changeset 19c888675e13
  add changeset 2a7f09cac94c
  adding manifests
  adding file changes
  adding f1.txt revisions
  added 2 changesets with 2 changes to 1 files
  invalid branchheads cache (served): tip differs
  rebase completed
  updating the branch cache
  truncating cache/rbc-revs-v1 to 72