tests/test-bheads.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

  $ heads()
  > {
  >    hg heads --template '{rev}: {desc|firstline|strip} ({branches})\n' "$@"
  > }

  $ hg init a
  $ cd a
  $ echo 'root' >root
  $ hg add root
  $ hg commit -m "Adding root node"
  $ heads
  0: Adding root node ()
-------
  $ heads .
  0: Adding root node ()

=======

  $ echo 'a' >a
  $ hg add a
  $ hg branch a
  marked working directory as branch a
  (branches are permanent and global, did you want a bookmark?)
  $ hg commit -m "Adding a branch"
  $ heads
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  1: Adding a branch (a)

=======

  $ hg update -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo 'b' >b
  $ hg add b
  $ hg branch b
  marked working directory as branch b
  $ hg commit -m "Adding b branch"
  $ heads
  2: Adding b branch (b)
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  2: Adding b branch (b)

=======

  $ echo 'bh1' >bh1
  $ hg add bh1
  $ hg commit -m "Adding b branch head 1"
  $ heads
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  3: Adding b branch head 1 (b)

=======

  $ hg update -C 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo 'bh2' >bh2
  $ hg add bh2
  $ hg commit -m "Adding b branch head 2"
  created new head
  $ heads
  4: Adding b branch head 2 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  $ heads .
  4: Adding b branch head 2 (b)
  3: Adding b branch head 1 (b)

=======

  $ hg update -C 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo 'bh3' >bh3
  $ hg add bh3
  $ hg commit -m "Adding b branch head 3"
  created new head
  $ heads
  5: Adding b branch head 3 (b)
  4: Adding b branch head 2 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  5: Adding b branch head 3 (b)
  4: Adding b branch head 2 (b)
  3: Adding b branch head 1 (b)

=======

  $ hg merge 4
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "Merging b branch head 2 and b branch head 3"
  $ heads
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)

=======

  $ echo 'c' >c
  $ hg add c
  $ hg branch c
  marked working directory as branch c
  $ hg commit -m "Adding c branch"
  $ heads
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
-------
  $ heads .
  7: Adding c branch (c)

=======

  $ heads -r 3 .
  no open branch heads found on branches c (started at 3)
  [1]
  $ heads -r 2 .
  7: Adding c branch (c)
-------
  $ hg update -C 4
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
-------
  $ heads -r 3 .
  3: Adding b branch head 1 (b)
-------
  $ heads -r 2 .
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
-------
  $ heads -r 7 .
  no open branch heads found on branches b (started at 7)
  [1]

=======

  $ for i in 0 1 2 3 4 5 6 7; do
  >     hg update -C "$i"
  >     heads
  >     echo '-------'
  >     heads .
  >     echo '-------'
  > done
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  0: Adding root node ()
  -------
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  1: Adding a branch (a)
  -------
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()
  -------
  7: Adding c branch (c)
  -------

=======

  $ for i in a b c z; do
  >     heads "$i"
  >     echo '-------'
  > done
  1: Adding a branch (a)
  -------
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  -------
  7: Adding c branch (c)
  -------
  abort: unknown revision 'z'!
  -------

=======

  $ heads 0 1 2 3 4 5 6 7
  7: Adding c branch (c)
  6: Merging b branch head 2 and b branch head 3 (b)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)
  0: Adding root node ()

Topological heads:

  $ heads -t
  7: Adding c branch (c)
  3: Adding b branch head 1 (b)
  1: Adding a branch (a)

  $ cd ..
______________

"created new head" message tests

  $ hg init newheadmsg
  $ cd newheadmsg

Init: no msg

  $ echo 1 > a
  $ hg ci -Am "a0: Initial root"
  adding a
  $ echo 2 >> a
  $ hg ci -m "a1 (HN)"

  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ echo 1 > b
  $ hg ci -Am "b2: Initial root for branch b"
  adding b
  $ echo 2 >> b
  $ hg ci -m "b3 (HN)"

Case NN: msg

  $ hg up -q null
  $ hg branch -f b
  marked working directory as branch b
  $ echo 1 > bb
  $ hg ci -Am "b4 (NN): new topo root for branch b"
  adding bb
  created new head

Case HN: no msg

  $ echo 2 >> bb
  $ hg ci -m "b5 (HN)"

Case BN: msg

  $ hg branch -f default
  marked working directory as branch default
  $ echo 1 > aa
  $ hg ci -Am "a6 (BN): new branch root"
  adding aa
  created new head

Case CN: msg

  $ hg up -q 4
  $ echo 3 >> bbb
  $ hg ci -Am "b7 (CN): regular new head"
  adding bbb
  created new head

Case BB: msg

  $ hg up -q 4
  $ hg merge -q 3
  $ hg branch -f default
  marked working directory as branch default
  $ hg ci -m "a8 (BB): weird new branch root"
  created new head

Case CB: msg

  $ hg up -q 4
  $ hg merge -q 1
  $ hg ci -m "b9 (CB): new head from branch merge"
  created new head

Case HB: no msg

  $ hg up -q 7
  $ hg merge -q 6
  $ hg ci -m "b10 (HB): continuing head from branch merge"

Case CC: msg

  $ hg up -q 4
  $ hg merge -q 2
  $ hg ci -m "b11 (CC): new head from merge"
  created new head

Case CH: no msg

  $ hg up -q 2
  $ hg merge -q 10
  $ hg ci -m "b12 (CH): continuing head from merge"

Case HH: no msg

  $ hg merge -q 3
  $ hg ci -m "b12 (HH): merging two heads"

  $ cd ..