annotate tests/test-graft.t @ 25591:f1d46075b13a

verify: check the subrepository references in .hgsubstate

While hopefully atypical, there are reasons that a subrepository revision can be
lost that aren't covered by corruption of the .hgsubstate revlog.  Such things
can happen when a subrepo is amended, stripped or simply isn't pulled from
upstream because the parent repo revision wasn't updated yet.  There's no way to
know if it is an error, but this will find potential problems sooner than when
some random revision is updated.

Until recently, convert made no attempt at rewriting the .hgsubstate file.  The
impetuous for this is to verify the conversion of some repositories, and this is
orders of magnitude faster than a bash script from 0..tip that does an
'hg update -C $rev'.  But it is equally useful to determine if everything has
been pulled down before taking a thumb drive on the go.

It feels somewhat wrong to leave this out of verifymod (mostly because the file
is already read in there, and the final summary is printed before the subrepos
are checked).  But verifymod looks very low level, so importing subrepo stuff
there seems more wrong.

Create a repo with some stuff in it:

  $ hg init a
  $ cd a
  $ echo a > a
  $ echo a > d
  $ echo a > e
  $ hg ci -qAm0
  $ echo b > a
  $ hg ci -m1 -u bar
  $ hg mv a b
  $ hg ci -m2
  $ hg cp b c
  $ hg ci -m3 -u baz
  $ echo b > d
  $ echo f > e
  $ hg ci -m4
  $ hg up -q 3
  $ echo b > e
  $ hg branch -q stable
  $ hg ci -m5
  $ hg merge -q default --tool internal:local
  $ hg branch -q default
  $ hg ci -m6
  $ hg phase --public 3
  $ hg phase --force --secret 6

  $ hg log -G --template '{author}@{rev}.{phase}: {desc}\n'
  @    [e-mail]: 6
  |\
  | o  [e-mail]: 5
  | |
  o |  [e-mail]: 4
  |/
  o  [e-mail]: 3
  |
  o  [e-mail]: 2
  |
  o  [e-mail]: 1
  |
  o  [e-mail]: 0
  

Need to specify a rev:

  $ hg graft
  abort: no revisions specified
  [255]

Can't graft ancestor:

  $ hg graft 1 2
  skipping ancestor revision 1:5d205f8b35b6
  skipping ancestor revision 2:5c095ad7e90f
  [255]

Specify revisions with -r:

  $ hg graft -r 1 -r 2
  skipping ancestor revision 1:5d205f8b35b6
  skipping ancestor revision 2:5c095ad7e90f
  [255]

  $ hg graft -r 1 2
  skipping ancestor revision 2:5c095ad7e90f
  skipping ancestor revision 1:5d205f8b35b6
  [255]

Can't graft with dirty wd:

  $ hg up -q 0
  $ echo foo > a
  $ hg graft 1
  abort: uncommitted changes
  [255]
  $ hg revert a

Graft a rename:
(this also tests that editor is invoked if '--edit' is specified)

  $ hg status --rev "2^1" --rev 2
  A b
  R a
  $ HGEDITOR=cat hg graft 2 -u foo --edit
  grafting 2:5c095ad7e90f "2"
  merging a and b to b
  2
  
  
  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
  HG: Leave message empty to abort commit.
  HG: --
  HG: user: foo
  HG: branch 'default'
  HG: added b
  HG: removed a
  $ hg export tip --git
  # HG changeset patch
  # User foo
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID ef0ef43d49e79e81ddafdc7997401ba0041efc82
  # Parent  68795b066622ca79a25816a662041d8f78f3cd9e
  2
  
  diff --git a/a b/b
  rename from a
  rename to b

Look for extra:source

  $ hg log --debug -r tip
  changeset:   7:ef0ef43d49e79e81ddafdc7997401ba0041efc82
  tag:         tip
  phase:       draft
  parent:      0:68795b066622ca79a25816a662041d8f78f3cd9e
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    7:e59b6b228f9cbf9903d5e9abf996e083a1f533eb
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  files+:      b
  files-:      a
  extra:       branch=default
  extra:       source=5c095ad7e90f871700f02dd1fa5012cb4498a2d4
  description:
  2
  
  

Graft out of order, skipping a merge and a duplicate
(this also tests that editor is not invoked if '--edit' is not specified)

  $ hg graft 1 5 4 3 'merge()' 2 -n
  skipping ungraftable merge revision 6
  skipping revision 2:5c095ad7e90f (already grafted to 7:ef0ef43d49e7)
  grafting 1:5d205f8b35b6 "1"
  grafting 5:97f8bfe72746 "5"
  grafting 4:9c233e8e184d "4"
  grafting 3:4c60f11aa304 "3"

  $ HGEDITOR=cat hg graft 1 5 4 3 'merge()' 2 --debug
  skipping ungraftable merge revision 6
  scanning for duplicate grafts
  skipping revision 2:5c095ad7e90f (already grafted to 7:ef0ef43d49e7)
  grafting 1:5d205f8b35b6 "1"
    searching for copies back to rev 1
    unmatched files in local:
     b
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: 'a' -> dst: 'b' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: 68795b066622, local: ef0ef43d49e7+, remote: 5d205f8b35b6
   preserving b for resolve of b
   b: local copied/moved from a -> m
  picked tool 'internal:merge' for b (binary False symlink False)
  merging b and a to b
  my b@ef0ef43d49e7+ other a@5d205f8b35b6 ancestor a@68795b066622
   premerge successful
  committing files:
  b
  committing manifest
  committing changelog
  grafting 5:97f8bfe72746 "5"
    searching for copies back to rev 1
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: 4c60f11aa304, local: 6b9e5368ca4e+, remote: 97f8bfe72746
   e: remote is newer -> g
  getting e
   b: remote unchanged -> k
  committing files:
  e
  committing manifest
  committing changelog
  grafting 4:9c233e8e184d "4"
    searching for copies back to rev 1
  resolving manifests
   branchmerge: True, force: True, partial: False
   ancestor: 4c60f11aa304, local: 1905859650ec+, remote: 9c233e8e184d
   preserving e for resolve of e
   d: remote is newer -> g
  getting d
   b: remote unchanged -> k
   e: versions differ -> m
  picked tool 'internal:merge' for e (binary False symlink False)
  merging e
  my e@1905859650ec+ other e@9c233e8e184d ancestor e@68795b066622
  warning: conflicts during merge.
  merging e incomplete! (edit conflicts, then use 'hg resolve --mark')
  abort: unresolved conflicts, can't continue
  (use hg resolve and hg graft --continue)
  [255]

Commit while interrupted should fail:

  $ hg ci -m 'commit interrupted graft'
  abort: graft in progress
  (use 'hg graft --continue' or 'hg update' to abort)
  [255]

Abort the graft and try committing:

  $ hg up -C .
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo c >> e
  $ hg ci -mtest

  $ hg strip . --config extensions.strip=
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/a/.hg/strip-backup/*-backup.hg (glob)

Graft again:

  $ hg graft 1 5 4 3 'merge()' 2
  skipping ungraftable merge revision 6
  skipping revision 2:5c095ad7e90f (already grafted to 7:ef0ef43d49e7)
  skipping revision 1:5d205f8b35b6 (already grafted to 8:6b9e5368ca4e)
  skipping revision 5:97f8bfe72746 (already grafted to 9:1905859650ec)
  grafting 4:9c233e8e184d "4"
  merging e
  warning: conflicts during merge.
  merging e incomplete! (edit conflicts, then use 'hg resolve --mark')
  abort: unresolved conflicts, can't continue
  (use hg resolve and hg graft --continue)
  [255]

Continue without resolve should fail:

  $ hg graft -c
  grafting 4:9c233e8e184d "4"
  abort: unresolved merge conflicts (see "hg help resolve")
  [255]

Fix up:

  $ echo b > e
  $ hg resolve -m e
  (no more unresolved files)

Continue with a revision should fail:

  $ hg graft -c 6
  abort: can't specify --continue and revisions
  [255]

  $ hg graft -c -r 6
  abort: can't specify --continue and revisions
  [255]

Continue for real, clobber usernames

  $ hg graft -c -U
  grafting 4:9c233e8e184d "4"
  grafting 3:4c60f11aa304 "3"

Compare with original:

  $ hg diff -r 6
  $ hg status --rev 0:. -C
  M d
  M e
  A b
    a
  A c
    a
  R a

View graph:

  $ hg log -G --template '{author}@{rev}.{phase}: {desc}\n'
  @  [e-mail]: 3
  |
  o  [e-mail]: 4
  |
  o  [e-mail]: 5
  |
  o  [e-mail]: 1
  |
  o  [e-mail]: 2
  |
  | o    [e-mail]: 6
  | |\
  | | o  [e-mail]: 5
  | | |
  | o |  [e-mail]: 4
  | |/
  | o  [e-mail]: 3
  | |
  | o  [e-mail]: 2
  | |
  | o  [e-mail]: 1
  |/
  o  [e-mail]: 0
  
Graft again onto another branch should preserve the original source
  $ hg up -q 0
  $ echo 'g'>g
  $ hg add g
  $ hg ci -m 7
  created new head
  $ hg graft 7
  grafting 7:ef0ef43d49e7 "2"

  $ hg log -r 7 --template '{rev}:{node}\n'
  7:ef0ef43d49e79e81ddafdc7997401ba0041efc82
  $ hg log -r 2 --template '{rev}:{node}\n'
  2:5c095ad7e90f871700f02dd1fa5012cb4498a2d4

  $ hg log --debug -r tip
  changeset:   13:7a4785234d87ec1aa420ed6b11afe40fa73e12a9
  tag:         tip
  phase:       draft
  parent:      12:b592ea63bb0c19a6c5c44685ee29a2284f9f1b8f
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    13:dc313617b8c32457c0d589e0dbbedfe71f3cd637
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  files+:      b
  files-:      a
  extra:       branch=default
  extra:       intermediate-source=ef0ef43d49e79e81ddafdc7997401ba0041efc82
  extra:       source=5c095ad7e90f871700f02dd1fa5012cb4498a2d4
  description:
  2
  
  
Disallow grafting an already grafted cset onto its original branch
  $ hg up -q 6
  $ hg graft 7
  skipping already grafted revision 7:ef0ef43d49e7 (was grafted from 2:5c095ad7e90f)
  [255]

Disallow grafting already grafted csets with the same origin onto each other
  $ hg up -q 13
  $ hg graft 2
  skipping revision 2:5c095ad7e90f (already grafted to 13:7a4785234d87)
  [255]
  $ hg graft 7
  skipping already grafted revision 7:ef0ef43d49e7 (13:7a4785234d87 also has origin 2:5c095ad7e90f)
  [255]

  $ hg up -q 7
  $ hg graft 2
  skipping revision 2:5c095ad7e90f (already grafted to 7:ef0ef43d49e7)
  [255]
  $ hg graft tip
  skipping already grafted revision 13:7a4785234d87 (7:ef0ef43d49e7 also has origin 2:5c095ad7e90f)
  [255]

Graft with --log

  $ hg up -Cq 1
  $ hg graft 3 --log -u foo
  grafting 3:4c60f11aa304 "3"
  warning: can't find ancestor for 'c' copied from 'b'!
  $ hg log --template '{rev} {parents} {desc}\n' -r tip
  14 1:5d205f8b35b6  3
  (grafted from 4c60f11aa304a54ae1c199feb94e7fc771e51ed8)

Resolve conflicted graft
  $ hg up -q 0
  $ echo b > a
  $ hg ci -m 8
  created new head
  $ echo c > a
  $ hg ci -m 9
  $ hg graft 1 --tool internal:fail
  grafting 1:5d205f8b35b6 "1"
  abort: unresolved conflicts, can't continue
  (use hg resolve and hg graft --continue)
  [255]
  $ hg resolve --all
  merging a
  warning: conflicts during merge.
  merging a incomplete! (edit conflicts, then use 'hg resolve --mark')
  [1]
  $ cat a
  <<<<<<< local: aaa4406d4f0a - test: 9
  c
  =======
  b
  >>>>>>> other: 5d205f8b35b6  - bar: 1
  $ echo b > a
  $ hg resolve -m a
  (no more unresolved files)
  $ hg graft -c
  grafting 1:5d205f8b35b6 "1"
  $ hg export tip --git
  # HG changeset patch
  # User bar
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID f67661df0c4804d301f064f332b57e7d5ddaf2be
  # Parent  aaa4406d4f0ae9befd6e58c82ec63706460cbca6
  1
  
  diff --git a/a b/a
  --- a/a
  +++ b/a
  @@ -1,1 +1,1 @@
  -c
  +b

Resolve conflicted graft with rename
  $ echo c > a
  $ hg ci -m 10
  $ hg graft 2 --tool internal:fail
  grafting 2:5c095ad7e90f "2"
  abort: unresolved conflicts, can't continue
  (use hg resolve and hg graft --continue)
  [255]
  $ hg resolve --all
  merging a and b to b
  (no more unresolved files)
  $ hg graft -c
  grafting 2:5c095ad7e90f "2"
  $ hg export tip --git
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 9627f653b421c61fc1ea4c4e366745070fa3d2bc
  # Parent  ee295f490a40b97f3d18dd4c4f1c8936c233b612
  2
  
  diff --git a/a b/b
  rename from a
  rename to b

Test simple origin(), with and without args
  $ hg log -r 'origin()'
  changeset:   1:5d205f8b35b6
  user:        bar
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     1
  
  changeset:   2:5c095ad7e90f
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   3:4c60f11aa304
  user:        baz
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     3
  
  changeset:   4:9c233e8e184d
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     4
  
  changeset:   5:97f8bfe72746
  branch:      stable
  parent:      3:4c60f11aa304
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     5
  
  $ hg log -r 'origin(7)'
  changeset:   2:5c095ad7e90f
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
Now transplant a graft to test following through copies
  $ hg up -q 0
  $ hg branch -q dev
  $ hg ci -qm "dev branch"
  $ hg --config extensions.transplant= transplant -q 7
  $ hg log -r 'origin(.)'
  changeset:   2:5c095ad7e90f
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
Test that the graft and transplant markers in extra are converted, allowing
origin() to still work.  Note that these recheck the immediately preceeding two
tests.
  $ hg --quiet --config extensions.convert= --config convert.hg.saverev=True convert . ../converted

The graft case
  $ hg -R ../converted log -r 7 --template "{rev}: {node}\n{join(extras, '\n')}\n"
  7: 7ae846e9111fc8f57745634250c7b9ac0a60689b
  branch=default
  convert_revision=ef0ef43d49e79e81ddafdc7997401ba0041efc82
  source=e0213322b2c1a5d5d236c74e79666441bee67a7d
  $ hg -R ../converted log -r 'origin(7)'
  changeset:   2:e0213322b2c1
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
Test that template correctly expands more than one 'extra' (issue4362), and that
'intermediate-source' is converted.
  $ hg -R ../converted log -r 13 --template "{extras % ' Extra: {extra}\n'}"
   Extra: branch=default
   Extra: convert_revision=7a4785234d87ec1aa420ed6b11afe40fa73e12a9
   Extra: intermediate-source=7ae846e9111fc8f57745634250c7b9ac0a60689b
   Extra: source=e0213322b2c1a5d5d236c74e79666441bee67a7d

The transplant case
  $ hg -R ../converted log -r tip --template "{rev}: {node}\n{join(extras, '\n')}\n"
  21: fbb6c5cc81002f2b4b49c9d731404688bcae5ade
  branch=dev
  convert_revision=7e61b508e709a11d28194a5359bc3532d910af21
  transplant_source=z\xe8F\xe9\x11\x1f\xc8\xf5wEcBP\xc7\xb9\xac (esc)
  `h\x9b (esc)
  $ hg -R ../converted log -r 'origin(tip)'
  changeset:   2:e0213322b2c1
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  

Test simple destination
  $ hg log -r 'destination()'
  changeset:   7:ef0ef43d49e7
  parent:      0:68795b066622
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   8:6b9e5368ca4e
  user:        bar
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     1
  
  changeset:   9:1905859650ec
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     5
  
  changeset:   10:52dc0b4c6907
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     4
  
  changeset:   11:882b35362a6b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     3
  
  changeset:   13:7a4785234d87
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   14:f64defefacee
  parent:      1:5d205f8b35b6
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     3
  
  changeset:   17:f67661df0c48
  user:        bar
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     1
  
  changeset:   19:9627f653b421
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   21:7e61b508e709
  branch:      dev
  tag:         tip
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  $ hg log -r 'destination(2)'
  changeset:   7:ef0ef43d49e7
  parent:      0:68795b066622
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   13:7a4785234d87
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   19:9627f653b421
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   21:7e61b508e709
  branch:      dev
  tag:         tip
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
Transplants of grafts can find a destination...
  $ hg log -r 'destination(7)'
  changeset:   21:7e61b508e709
  branch:      dev
  tag:         tip
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
... grafts of grafts unfortunately can't
  $ hg graft -q 13
  warning: can't find ancestor for 'b' copied from 'a'!
  $ hg log -r 'destination(13)'
All copies of a cset
  $ hg log -r 'origin(13) or destination(origin(13))'
  changeset:   2:5c095ad7e90f
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   7:ef0ef43d49e7
  parent:      0:68795b066622
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   13:7a4785234d87
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   19:9627f653b421
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   21:7e61b508e709
  branch:      dev
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   22:d1cb6591fa4b
  branch:      dev
  tag:         tip
  user:        foo
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  

graft works on complex revset

  $ hg graft 'origin(13) or destination(origin(13))'
  skipping ancestor revision 21:7e61b508e709
  skipping ancestor revision 22:d1cb6591fa4b
  skipping revision 2:5c095ad7e90f (already grafted to 22:d1cb6591fa4b)
  grafting 7:ef0ef43d49e7 "2"
  warning: can't find ancestor for 'b' copied from 'a'!
  grafting 13:7a4785234d87 "2"
  warning: can't find ancestor for 'b' copied from 'a'!
  grafting 19:9627f653b421 "2"
  merging b
  warning: can't find ancestor for 'b' copied from 'a'!

graft with --force (still doesn't graft merges)

  $ hg graft 19 0 6
  skipping ungraftable merge revision 6
  skipping ancestor revision 0:68795b066622
  skipping already grafted revision 19:9627f653b421 (22:d1cb6591fa4b also has origin 2:5c095ad7e90f)
  [255]
  $ hg graft 19 0 6 --force
  skipping ungraftable merge revision 6
  grafting 19:9627f653b421 "2"
  merging b
  warning: can't find ancestor for 'b' copied from 'a'!
  grafting 0:68795b066622 "0"

graft --force after backout

  $ echo abc > a
  $ hg ci -m 28
  $ hg backout 28
  reverting a
  changeset 29:53177ba928f6 backs out changeset 28:50a516bb8b57
  $ hg graft 28
  skipping ancestor revision 28:50a516bb8b57
  [255]
  $ hg graft 28 --force
  grafting 28:50a516bb8b57 "28"
  merging a
  $ cat a
  abc

graft --continue after --force

  $ echo def > a
  $ hg ci -m 31
  $ hg graft 28 --force --tool internal:fail
  grafting 28:50a516bb8b57 "28"
  abort: unresolved conflicts, can't continue
  (use hg resolve and hg graft --continue)
  [255]
  $ hg resolve --all
  merging a
  warning: conflicts during merge.
  merging a incomplete! (edit conflicts, then use 'hg resolve --mark')
  [1]
  $ echo abc > a
  $ hg resolve -m a
  (no more unresolved files)
  $ hg graft -c
  grafting 28:50a516bb8b57 "28"
  $ cat a
  abc

Continue testing same origin policy, using revision numbers from test above
but do some destructive editing of the repo:

  $ hg up -qC 7
  $ hg tag -l -r 13 tmp
  $ hg --config extensions.strip= strip 2
  saved backup bundle to $TESTTMP/a/.hg/strip-backup/5c095ad7e90f-d323a1e4-backup.hg (glob)
  $ hg graft tmp
  skipping already grafted revision 8:7a4785234d87 (2:ef0ef43d49e7 also has unknown origin 5c095ad7e90f)
  [255]

Empty graft

  $ hg up -qr 26
  $ hg tag -f something
  $ hg graft -qr 27
  $ hg graft -f 27
  grafting 27:ed6c7e54e319 "28"
  note: graft of 27:ed6c7e54e319 created no changes to commit

  $ cd ..

Graft to duplicate a commit

  $ hg init graftsibling
  $ cd graftsibling
  $ touch a
  $ hg commit -qAm a
  $ touch b
  $ hg commit -qAm b
  $ hg log -G -T '{rev}\n'
  @  1
  |
  o  0
  
  $ hg up -q 0
  $ hg graft -r 1
  grafting 1:0e067c57feba "b" (tip)
  $ hg log -G -T '{rev}\n'
  @  2
  |
  | o  1
  |/
  o  0
  
Graft to duplicate a commit twice

  $ hg up -q 0
  $ hg graft -r 2
  grafting 2:044ec77f6389 "b" (tip)
  $ hg log -G -T '{rev}\n'
  @  3
  |
  | o  2
  |/
  | o  1
  |/
  o  0