view tests/test-obsolete-divergent.t @ 40326:fed697fa1734

sqlitestore: file storage backend using SQLite

This commit provides an extension which uses SQLite to store file
data (as opposed to revlogs).

As the inline documentation describes, there are still several
aspects to the extension that are incomplete. But it's a start.
The extension does support basic clone, checkout, and commit
workflows, which makes it suitable for simple use cases.

One notable missing feature is support for "bundlerepos." This is
probably responsible for the most test failures when the extension
is activated as part of the test suite.

All revision data is stored in SQLite. Data is stored as zstd
compressed chunks (default if zstd is available), zlib compressed
chunks (default if zstd is not available), or raw chunks (if
configured or if a compressed delta is not smaller than the raw
delta). This makes things very similar to revlogs.

Unlike revlogs, the extension doesn't yet enforce a limit on delta
chain length. This is an obvious limitation and should be addressed.
This is somewhat mitigated by the use of zstd, which is much faster
than zlib to decompress.

There is a dedicated table for storing deltas. Deltas are stored
by the SHA-1 hash of their uncompressed content. The "fileindex" table
has columns that reference the delta for each revision and the base
delta that delta should be applied against. A recursive SQL query
is used to resolve the delta chain along with the delta data.

By storing deltas by hash, we are able to de-duplicate delta storage!
With revlogs, the same deltas in different revlogs would result in
duplicate storage of that delta. In this scheme, inserting the
duplicate delta is a no-op and delta chains simply reference the
existing delta.

When initially implementing this extension, I did not have
content-indexed deltas and deltas could be duplicated across files
(just like revlogs). When I implemented content-indexed deltas, the
size of the SQLite database for a full clone of mozilla-unified
dropped:

before: 2,554,261,504 bytes
after:  2,488,754,176 bytes

Surprisingly, this is still larger than the bytes size of revlog
files:

revlog files: 2,104,861,230 bytes
du -b:        2,254,381,614

I would have expected storage to be smaller since we're not limiting
delta chain length and since we're using zstd instead of zlib. I
suspect the SQLite indexes and per-column overhead account for the
bulk of the differences. (Keep in mind that revlog uses a 64-byte
packed struct for revision index data and deltas are stored without
padding. Aside from the 12 unused bytes in the 32 byte node field,
revlogs are pretty efficient.) Another source of overhead is file
name storage. With revlogs, file names are stored in the filesystem.
But with SQLite, we need to store file names in the database. This is
roughly equivalent to the size of the fncache file, which for the
mozilla-unified repository is ~34MB.

Since the SQLite database isn't append-only and since delta chains
can reference any delta, this opens some interesting possibilities.
For example, we could store deltas in reverse, such that fulltexts
are stored for newer revisions and deltas are applied to reconstruct
older revisions. This is likely a more optimal storage strategy for
version control, as new data tends to be more frequently accessed
than old data. We would obviously need wire protocol support for
transferring revision data from newest to oldest. And we would
probably need some kind of mechanism for "re-encoding" stores. But
it should be doable.

This extension is very much experimental quality. There are a handful
of features that don't work. It probably isn't suitable for day-to-day
use. But it could be used in limited cases (e.g. read-only checkouts
like in CI). And it is also a good proving ground for alternate
storage backends. As we continue to define interfaces for all things
storage, it will be useful to have a viable alternate storage backend
to see how things shake out in practice.

test-storage.py passes on Python 2 and introduces no new test failures on
Python 3. Having the storage-level unit tests has proved to be insanely
useful when developing this extension. Those tests caught numerous bugs
during development and I'm convinced this style of testing is the way
forward for ensuring alternate storage backends work as intended. Of
course, test coverage isn't close to what it needs to be. But it is
a start. And what coverage we have gives me confidence that basic store
functionality is implemented properly.

Differential Revision: https://phab.mercurial-scm.org/D4928

Test file dedicated to testing the divergent troubles from obsolete changeset.

This is the most complex troubles from far so we isolate it in a dedicated
file.

Enable obsolete

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > logtemplate = {rev}:{node|short} {desc}{if(obsfate, " [{join(obsfate, "; ")}]")}\n
  > [experimental]
  > evolution.createmarkers=True
  > [extensions]
  > drawdag=$TESTDIR/drawdag.py
  > [alias]
  > debugobsolete = debugobsolete -d '0 0'
  > [phases]
  > publish=False
  > [templates]
  > wuentryshort = '{instability}:{if(divergentnodes, " ")}{divergentnodes} {reason} {node|shortest}\n'
  > whyunstableshort = '{whyunstable % wuentryshort}'
  > wuentryshorter = '{instability}:{divergentnodes % " {node|shortest} ({phase})"} {reason} {node|shortest}\n'
  > whyunstableshorter = '{whyunstable % wuentryshorter}'
  > EOF


  $ mkcommit() {
  >    echo "$1" > "$1"
  >    hg add "$1"
  >    hg ci -m "$1"
  > }
  $ getid() {
  >    hg log --hidden -r "desc('$1')" -T '{node}\n'
  > }

setup repo

  $ hg init reference
  $ cd reference
  $ mkcommit base
  $ mkcommit A_0
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A_1
  created new head
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A_2
  created new head
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ cd ..


  $ newcase() {
  >    hg clone -u 0 -q reference $1
  >    cd $1
  > }

direct divergence
-----------------

A_1 have two direct and divergent successors A_1 and A_1

  $ newcase direct
  $ hg debugobsolete `getid A_0` `getid A_1`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_0` `getid A_2`
  2 new content-divergent changesets
  $ hg log -G --hidden
  *  3:392fd25390da A_2
  |
  | *  2:82623d38b9ba A_1
  |/
  | x  1:007dc284c1f8 A_0 [rewritten as 2:82623d38b9ba; rewritten as 3:392fd25390da]
  |/
  @  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg log -r 'contentdivergent()'
  2:82623d38b9ba A_1
  3:392fd25390da A_2
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da

check that mercurial refuse to push

  $ hg init ../other
  $ hg push ../other
  pushing to ../other
  searching for changes
  abort: push includes content-divergent changeset: 392fd25390da!
  [255]

  $ cd ..


indirect divergence with known changeset
-------------------------------------------

  $ newcase indirect_known
  $ hg debugobsolete `getid A_0` `getid A_1`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_0` `getid A_2`
  2 new content-divergent changesets
  $ mkcommit A_3
  created new head
  $ hg debugobsolete `getid A_2` `getid A_3`
  obsoleted 1 changesets
  $ hg log -G --hidden
  @  4:01f36c5a8fda A_3
  |
  | x  3:392fd25390da A_2 [rewritten as 4:01f36c5a8fda]
  |/
  | *  2:82623d38b9ba A_1
  |/
  | x  1:007dc284c1f8 A_0 [rewritten as 2:82623d38b9ba; rewritten as 3:392fd25390da]
  |/
  o  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      01f36c5a8fda
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      01f36c5a8fda
  01f36c5a8fda
      01f36c5a8fda
  $ hg log -r 'contentdivergent()'
  2:82623d38b9ba A_1
  4:01f36c5a8fda A_3
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  82623d38b9ba
      82623d38b9ba
  01f36c5a8fda
      01f36c5a8fda
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  01f36c5a8fda
      01f36c5a8fda
  $ cd ..


indirect divergence with known changeset
-------------------------------------------

  $ newcase indirect_unknown
  $ hg debugobsolete `getid A_0` aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
  obsoleted 1 changesets
  $ hg debugobsolete aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa `getid A_1`
  $ hg debugobsolete `getid A_0` `getid A_2`
  2 new content-divergent changesets
  $ hg log -G --hidden
  *  3:392fd25390da A_2
  |
  | *  2:82623d38b9ba A_1
  |/
  | x  1:007dc284c1f8 A_0 [rewritten as 2:82623d38b9ba; rewritten as 3:392fd25390da]
  |/
  @  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg log -r 'contentdivergent()'
  2:82623d38b9ba A_1
  3:392fd25390da A_2
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ cd ..

do not take unknown node in account if they are final
-----------------------------------------------------

  $ newcase final-unknown
  $ hg debugobsolete `getid A_0` `getid A_1`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_1` `getid A_2`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_0` bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  $ hg debugobsolete bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb cccccccccccccccccccccccccccccccccccccccc
  $ hg debugobsolete `getid A_1` dddddddddddddddddddddddddddddddddddddddd

  $ hg debugsuccessorssets --hidden 'desc('A_0')'
  007dc284c1f8
      392fd25390da
  $ hg debugsuccessorssets 'desc('A_0')' --closest
  $ hg debugsuccessorssets 'desc('A_0')' --closest --hidden
  007dc284c1f8
      82623d38b9ba

  $ cd ..

divergence that converge again is not divergence anymore
-----------------------------------------------------

  $ newcase converged_divergence
  $ hg debugobsolete `getid A_0` `getid A_1`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_0` `getid A_2`
  2 new content-divergent changesets
  $ mkcommit A_3
  created new head
  $ hg debugobsolete `getid A_1` `getid A_3`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_2` `getid A_3`
  obsoleted 1 changesets
  $ hg log -G --hidden
  @  4:01f36c5a8fda A_3
  |
  | x  3:392fd25390da A_2 [rewritten as 4:01f36c5a8fda]
  |/
  | x  2:82623d38b9ba A_1 [rewritten as 4:01f36c5a8fda]
  |/
  | x  1:007dc284c1f8 A_0 [rewritten as 2:82623d38b9ba; rewritten as 3:392fd25390da]
  |/
  o  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      01f36c5a8fda
  82623d38b9ba
      01f36c5a8fda
  392fd25390da
      01f36c5a8fda
  01f36c5a8fda
      01f36c5a8fda
  $ hg log -r 'contentdivergent()'
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  01f36c5a8fda
      01f36c5a8fda
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba
      392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  01f36c5a8fda
      01f36c5a8fda
  $ cd ..

split is not divergences
-----------------------------

  $ newcase split
  $ hg debugobsolete `getid A_0` `getid A_1` `getid A_2`
  obsoleted 1 changesets
  $ hg log -G --hidden
  o  3:392fd25390da A_2
  |
  | o  2:82623d38b9ba A_1
  |/
  | x  1:007dc284c1f8 A_0 [split as 2:82623d38b9ba, 3:392fd25390da]
  |/
  @  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba 392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg log -r 'contentdivergent()'
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba 392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da

Even when subsequent rewriting happen

  $ mkcommit A_3
  created new head
  $ hg debugobsolete `getid A_1` `getid A_3`
  obsoleted 1 changesets
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A_4
  created new head
  $ hg debugobsolete `getid A_2` `getid A_4`
  obsoleted 1 changesets
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A_5
  created new head
  $ hg debugobsolete `getid A_4` `getid A_5`
  obsoleted 1 changesets
  $ hg log -G --hidden
  @  6:e442cfc57690 A_5
  |
  | x  5:6a411f0d7a0a A_4 [rewritten as 6:e442cfc57690]
  |/
  | o  4:01f36c5a8fda A_3
  |/
  | x  3:392fd25390da A_2 [rewritten as 5:6a411f0d7a0a]
  |/
  | x  2:82623d38b9ba A_1 [rewritten as 4:01f36c5a8fda]
  |/
  | x  1:007dc284c1f8 A_0 [split as 2:82623d38b9ba, 3:392fd25390da]
  |/
  o  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      01f36c5a8fda e442cfc57690
  82623d38b9ba
      01f36c5a8fda
  392fd25390da
      e442cfc57690
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      e442cfc57690
  e442cfc57690
      e442cfc57690
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  01f36c5a8fda
      01f36c5a8fda
  e442cfc57690
      e442cfc57690
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba 392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      e442cfc57690
  e442cfc57690
      e442cfc57690
  $ hg log -r 'contentdivergent()'

Check more complex obsolescence graft (with divergence)

  $ mkcommit B_0; hg up 0
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg debugobsolete `getid B_0` `getid A_2`
  obsoleted 1 changesets
  $ mkcommit A_7; hg up 0
  created new head
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A_8; hg up 0
  created new head
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg debugobsolete `getid A_5` `getid A_7` `getid A_8`
  obsoleted 1 changesets
  $ mkcommit A_9; hg up 0
  created new head
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg debugobsolete `getid A_5` `getid A_9`
  4 new content-divergent changesets
  $ hg log -G --hidden
  *  10:bed64f5d2f5a A_9
  |
  | *  9:14608b260df8 A_8
  |/
  | *  8:7ae126973a96 A_7
  |/
  | x  7:3750ebee865d B_0 [rewritten as 3:392fd25390da]
  | |
  | x  6:e442cfc57690 A_5 [rewritten as 10:bed64f5d2f5a; split as 8:7ae126973a96, 9:14608b260df8]
  |/
  | x  5:6a411f0d7a0a A_4 [rewritten as 6:e442cfc57690]
  |/
  | *  4:01f36c5a8fda A_3
  |/
  | x  3:392fd25390da A_2 [rewritten as 5:6a411f0d7a0a]
  |/
  | x  2:82623d38b9ba A_1 [rewritten as 4:01f36c5a8fda]
  |/
  | x  1:007dc284c1f8 A_0 [split as 2:82623d38b9ba, 3:392fd25390da]
  |/
  @  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      01f36c5a8fda bed64f5d2f5a
      01f36c5a8fda 7ae126973a96 14608b260df8
  82623d38b9ba
      01f36c5a8fda
  392fd25390da
      bed64f5d2f5a
      7ae126973a96 14608b260df8
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      bed64f5d2f5a
      7ae126973a96 14608b260df8
  e442cfc57690
      bed64f5d2f5a
      7ae126973a96 14608b260df8
  3750ebee865d
      bed64f5d2f5a
      7ae126973a96 14608b260df8
  7ae126973a96
      7ae126973a96
  14608b260df8
      14608b260df8
  bed64f5d2f5a
      bed64f5d2f5a
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  01f36c5a8fda
      01f36c5a8fda
  7ae126973a96
      7ae126973a96
  14608b260df8
      14608b260df8
  bed64f5d2f5a
      bed64f5d2f5a
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba 392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      e442cfc57690
  e442cfc57690
      e442cfc57690
  3750ebee865d
      392fd25390da
  7ae126973a96
      7ae126973a96
  14608b260df8
      14608b260df8
  bed64f5d2f5a
      bed64f5d2f5a
  $ hg log -r 'contentdivergent()'
  4:01f36c5a8fda A_3
  8:7ae126973a96 A_7
  9:14608b260df8 A_8
  10:bed64f5d2f5a A_9

  $ hg log -r bed64f5d2f5a -T '{whyunstable}\n' | sort
  content-divergent: 4:01f36c5a8fda (draft) 8:7ae126973a96 (draft) 9:14608b260df8 (draft) predecessor 007dc284c1f8
  content-divergent: 8:7ae126973a96 (draft) 9:14608b260df8 (draft) predecessor e442cfc57690
  $ hg log -r bed64f5d2f5a -T whyunstableshort | sort
  content-divergent: 4:01f36c5a8fda (draft) 8:7ae126973a96 (draft) 9:14608b260df8 (draft) predecessor 007d
  content-divergent: 8:7ae126973a96 (draft) 9:14608b260df8 (draft) predecessor e442
  $ hg log -r bed64f5d2f5a -T whyunstableshorter | sort
  content-divergent: 01f3 (draft) 7ae1 (draft) 1460 (draft) predecessor 007d
  content-divergent: 7ae1 (draft) 1460 (draft) predecessor e442

fix the divergence

  $ mkcommit A_A; hg up 0
  created new head
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg debugobsolete `getid A_9` `getid A_A`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_7` `getid A_A`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_8` `getid A_A`
  obsoleted 1 changesets
  $ hg log -G --hidden
  o  11:a139f71be9da A_A
  |
  | x  10:bed64f5d2f5a A_9 [rewritten as 11:a139f71be9da]
  |/
  | x  9:14608b260df8 A_8 [rewritten as 11:a139f71be9da]
  |/
  | x  8:7ae126973a96 A_7 [rewritten as 11:a139f71be9da]
  |/
  | x  7:3750ebee865d B_0 [rewritten as 3:392fd25390da]
  | |
  | x  6:e442cfc57690 A_5 [rewritten as 10:bed64f5d2f5a; split as 8:7ae126973a96, 9:14608b260df8]
  |/
  | x  5:6a411f0d7a0a A_4 [rewritten as 6:e442cfc57690]
  |/
  | o  4:01f36c5a8fda A_3
  |/
  | x  3:392fd25390da A_2 [rewritten as 5:6a411f0d7a0a]
  |/
  | x  2:82623d38b9ba A_1 [rewritten as 4:01f36c5a8fda]
  |/
  | x  1:007dc284c1f8 A_0 [split as 2:82623d38b9ba, 3:392fd25390da]
  |/
  @  0:d20a80d4def3 base
  
  $ hg debugsuccessorssets --hidden 'all()'
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      01f36c5a8fda a139f71be9da
  82623d38b9ba
      01f36c5a8fda
  392fd25390da
      a139f71be9da
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      a139f71be9da
  e442cfc57690
      a139f71be9da
  3750ebee865d
      a139f71be9da
  7ae126973a96
      a139f71be9da
  14608b260df8
      a139f71be9da
  bed64f5d2f5a
      a139f71be9da
  a139f71be9da
      a139f71be9da
  $ hg debugsuccessorssets 'all()' --closest
  d20a80d4def3
      d20a80d4def3
  01f36c5a8fda
      01f36c5a8fda
  a139f71be9da
      a139f71be9da
  $ hg debugsuccessorssets 'all()' --closest --hidden
  d20a80d4def3
      d20a80d4def3
  007dc284c1f8
      82623d38b9ba 392fd25390da
  82623d38b9ba
      82623d38b9ba
  392fd25390da
      392fd25390da
  01f36c5a8fda
      01f36c5a8fda
  6a411f0d7a0a
      e442cfc57690
  e442cfc57690
      e442cfc57690
  3750ebee865d
      392fd25390da
  7ae126973a96
      a139f71be9da
  14608b260df8
      a139f71be9da
  bed64f5d2f5a
      a139f71be9da
  a139f71be9da
      a139f71be9da
  $ hg log -r 'contentdivergent()'

#if serve

  $ hg serve -n test -p $HGPORT -d --pid-file=hg.pid --config web.view=all \
  >   -A access.log -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS

check an obsolete changeset that was rewritten and also split

  $ get-with-headers.py localhost:$HGPORT 'rev/e442cfc57690?style=paper' | egrep 'rewritten|split'
   <td>rewritten as <a href="/rev/bed64f5d2f5a?style=paper">bed64f5d2f5a</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span><br>
  split as <a href="/rev/7ae126973a96?style=paper">7ae126973a96</a> <a href="/rev/14608b260df8?style=paper">14608b260df8</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/e442cfc57690?style=coal' | egrep 'rewritten|split'
   <td>rewritten as <a href="/rev/bed64f5d2f5a?style=coal">bed64f5d2f5a</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span><br>
  split as <a href="/rev/7ae126973a96?style=coal">7ae126973a96</a> <a href="/rev/14608b260df8?style=coal">14608b260df8</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/e442cfc57690?style=gitweb' | egrep 'rewritten|split'
  <td>rewritten as <a class="list" href="/rev/bed64f5d2f5a?style=gitweb">bed64f5d2f5a</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>
  <td>split as <a class="list" href="/rev/7ae126973a96?style=gitweb">7ae126973a96</a> <a class="list" href="/rev/14608b260df8?style=gitweb">14608b260df8</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/e442cfc57690?style=monoblue' | egrep 'rewritten|split'
  <dd>rewritten as <a href="/rev/bed64f5d2f5a?style=monoblue">bed64f5d2f5a</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></dd>
  <dd>split as <a href="/rev/7ae126973a96?style=monoblue">7ae126973a96</a> <a href="/rev/14608b260df8?style=monoblue">14608b260df8</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></dd>
  $ get-with-headers.py localhost:$HGPORT 'rev/e442cfc57690?style=spartan' | egrep 'rewritten|split'
  <td class="obsolete">rewritten as <a href="/rev/bed64f5d2f5a?style=spartan">bed64f5d2f5a</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>
  <td class="obsolete">split as <a href="/rev/7ae126973a96?style=spartan">7ae126973a96</a> <a href="/rev/14608b260df8?style=spartan">14608b260df8</a>  by &#116;&#101;&#115;&#116; <span class="age">Thu, 01 Jan 1970 00:00:00 +0000</span></td>

  $ killdaemons.py

#endif

  $ cd ..


Subset does not diverge
------------------------------

Do not report divergent successors-set if it is a subset of another
successors-set. (report [A,B] not [A] + [A,B])

  $ newcase subset
  $ hg debugobsolete `getid A_0` `getid A_2`
  obsoleted 1 changesets
  $ hg debugobsolete `getid A_0` `getid A_1` `getid A_2`
  $ hg debugsuccessorssets --hidden 'desc('A_0')'
  007dc284c1f8
      82623d38b9ba 392fd25390da
  $ hg debugsuccessorssets 'desc('A_0')' --closest
  $ hg debugsuccessorssets 'desc('A_0')' --closest --hidden
  007dc284c1f8
      82623d38b9ba 392fd25390da

  $ cd ..

Use scmutil.cleanupnodes API to create divergence

  $ hg init cleanupnodes
  $ cd cleanupnodes
  $ hg debugdrawdag <<'EOS'
  >   B1  B3 B4
  >   |     \|
  >   A      Z
  > EOS

  $ hg update -q B1
  $ echo 3 >> B
  $ hg commit --amend -m B2
  $ cat > $TESTTMP/scmutilcleanup.py <<EOF
  > from mercurial import registrar, scmutil
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command(b'cleanup')
  > def cleanup(ui, repo):
  >     def node(expr):
  >         unfi = repo.unfiltered()
  >         rev = unfi.revs(expr).first()
  >         return unfi.changelog.node(rev)
  >     with repo.wlock(), repo.lock(), repo.transaction(b'delayedstrip'):
  >         mapping = {node(b'desc(B1)'): [node(b'desc(B3)')],
  >                    node(b'desc(B3)'): [node(b'desc(B4)')]}
  >         scmutil.cleanupnodes(repo, mapping, b'test')
  > EOF

  $ rm .hg/localtags
  $ hg cleanup --config extensions.t=$TESTTMP/scmutilcleanup.py
  2 new content-divergent changesets
  $ hg log -G -T '{rev}:{node|short} {desc} {instabilities}' -r 'sort(all(), topo)'
  @  5:1a2a9b5b0030 B2 content-divergent
  |
  | *  4:70d5a63ca112 B4 content-divergent
  | |
  | o  1:48b9aae0607f Z
  |
  o  0:426bada5c675 A
  
  $ hg debugobsolete
  a178212c3433c4e77b573f6011e29affb8aefa33 1a2a9b5b0030632400aa78e00388c20f99d3ec44 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '1', 'operation': 'amend', 'user': 'test'}
  a178212c3433c4e77b573f6011e29affb8aefa33 ad6478fb94ecec98b86daae98722865d494ac561 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '13', 'operation': 'test', 'user': 'test'}
  ad6478fb94ecec98b86daae98722865d494ac561 70d5a63ca112acb3764bc1d7320ca90ea688d671 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '9', 'operation': 'test', 'user': 'test'}

  $ hg debugwhyunstable 1a2a9b5b0030
  content-divergent: 70d5a63ca112acb3764bc1d7320ca90ea688d671 (draft) predecessor a178212c3433c4e77b573f6011e29affb8aefa33

  $ hg log -r 1a2a9b5b0030 -T '{whyunstable}\n'
  content-divergent: 4:70d5a63ca112 (draft) predecessor a178212c3433
  $ hg log -r 1a2a9b5b0030 -T whyunstableshort
  content-divergent: 4:70d5a63ca112 (draft) predecessor a178
  $ hg log -r 1a2a9b5b0030 -T whyunstableshorter
  content-divergent: 70d5 (draft) predecessor a178

#if serve

  $ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS

check explanation for a content-divergent changeset

  $ get-with-headers.py localhost:$HGPORT 'rev/1a2a9b5b0030?style=paper' | grep divergent:
   <td>content-divergent: <a href="/rev/70d5a63ca112?style=paper">70d5a63ca112</a> (draft) predecessor <a href="/rev/a178212c3433?style=paper">a178212c3433</a></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/1a2a9b5b0030?style=coal' | grep divergent:
   <td>content-divergent: <a href="/rev/70d5a63ca112?style=coal">70d5a63ca112</a> (draft) predecessor <a href="/rev/a178212c3433?style=coal">a178212c3433</a></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/1a2a9b5b0030?style=gitweb' | grep divergent:
  <td>content-divergent: <a class="list" href="/rev/70d5a63ca112?style=gitweb">70d5a63ca112</a> (draft) predecessor <a class="list" href="/rev/a178212c3433?style=gitweb">a178212c3433</a></td>
  $ get-with-headers.py localhost:$HGPORT 'rev/1a2a9b5b0030?style=monoblue' | grep divergent:
  <dd>content-divergent: <a href="/rev/70d5a63ca112?style=monoblue">70d5a63ca112</a> (draft) predecessor <a href="/rev/a178212c3433?style=monoblue">a178212c3433</a></dd>
  $ get-with-headers.py localhost:$HGPORT 'rev/1a2a9b5b0030?style=spartan' | grep divergent:
  <td class="unstable">content-divergent: <a href="/rev/70d5a63ca112?style=spartan">70d5a63ca112</a> (draft) predecessor <a href="/rev/a178212c3433?style=spartan">a178212c3433</a></td>

  $ killdaemons.py

#endif