view tests/test-merge-default.t @ 36672:9e7b14caf67f

xdiff: remove patience and histogram diff algorithms

Patience diff is the normal diff algorithm, plus some greediness that
unconditionally matches common common unique lines.  That means it is easy to
construct cases to let it generate suboptimal result, like:

```
open('a', 'w').write('\n'.join(list('a' + 'x' * 300 + 'u' + 'x' * 700 + 'a\n')))
open('b', 'w').write('\n'.join(list('b' + 'x' * 700 + 'u' + 'x' * 300 + 'b\n')))
```

Patience diff has been advertised as being able to generate better results for
some C code changes. However, the more scientific way to do that is the
indention heuristic [1].

Since patience diff could generate suboptimal result more easily and its
"better" diff feature could be replaced by the new indention heuristic, let's
just remove it and its variant histogram diff to simplify the code.

[1]: https://github.com/git/git/commit/433860f3d0beb0c6f205290bd16cda413148f098

Test Plan:
`gcc -fPIC *.c --shared -o xdiff.so` still builds.

Differential Revision: https://phab.mercurial-scm.org/D2573

  $ hg init
  $ echo a > a
  $ hg commit -A -ma
  adding a

  $ echo b >> a
  $ hg commit -mb

  $ echo c >> a
  $ hg commit -mc

  $ hg up 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo d >> a
  $ hg commit -md
  created new head

  $ hg up 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo e >> a
  $ hg commit -me
  created new head

  $ hg up 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Should fail because not at a head:

  $ hg merge
  abort: working directory not at a head revision
  (use 'hg update' or merge with an explicit revision)
  [255]

  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "f25cbe84d8b3: e"
  2 other heads for branch "default"

Should fail because > 2 heads:

  $ HGMERGE=internal:other; export HGMERGE
  $ hg merge
  abort: branch 'default' has 3 heads - please merge with an explicit rev
  (run 'hg heads .' to see heads)
  [255]

Should succeed:

  $ hg merge 2
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg id -Tjson
  [
   {
    "bookmarks": [],
    "branch": "default",
    "dirty": "+",
    "id": "f25cbe84d8b3+2d95304fed5d+",
    "node": "ffffffffffffffffffffffffffffffffffffffff",
    "parents": [{"node": "f25cbe84d8b320e298e7703f18a25a3959518c23", "rev": 4}, {"node": "2d95304fed5d89bc9d70b2a0d02f0d567469c3ab", "rev": 2}],
    "tags": ["tip"]
   }
  ]
  $ hg commit -mm1

Should succeed - 2 heads:

  $ hg merge -P
  changeset:   3:ea9ff125ff88
  parent:      1:1846eede8b68
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     d
  
  $ hg merge
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -mm2

  $ hg id -r 1 -Tjson
  [
   {
    "bookmarks": [],
    "branch": "default",
    "id": "1846eede8b68",
    "node": "1846eede8b6886d8cc8a88c96a687b7fe8f3b9d1",
    "tags": []
   }
  ]

Should fail because at tip:

  $ hg merge
  abort: nothing to merge
  [255]

  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Should fail because there is only one head:

  $ hg merge
  abort: nothing to merge
  (use 'hg update' instead)
  [255]

  $ hg up 3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo f >> a
  $ hg branch foobranch
  marked working directory as branch foobranch
  (branches are permanent and global, did you want a bookmark?)
  $ hg commit -mf

Should fail because merge with other branch:

  $ hg merge
  abort: branch 'foobranch' has one head - please merge with an explicit rev
  (run 'hg heads' to see all heads)
  [255]


Test for issue2043: ensure that 'merge -P' shows ancestors of 6 that
are not ancestors of 7, regardless of where their common ancestors are.

Merge preview not affected by common ancestor:

  $ hg up -q 7
  $ hg merge -q -P 6
  2:2d95304fed5d
  4:f25cbe84d8b3
  5:a431fabd6039
  6:e88e33f3bf62

Test experimental destination revset

  $ hg log -r '_destmerge()'
  abort: branch 'foobranch' has one head - please merge with an explicit rev
  (run 'hg heads' to see all heads)
  [255]

(on a branch with a two heads)

  $ hg up 5
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo f >> a
  $ hg commit -mf
  created new head
  $ hg log -r '_destmerge()'
  changeset:   6:e88e33f3bf62
  parent:      5:a431fabd6039
  parent:      3:ea9ff125ff88
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     m2
  

(from the other head)

  $ hg log -r '_destmerge(e88e33f3bf62)'
  changeset:   8:b613918999e2
  tag:         tip
  parent:      5:a431fabd6039
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     f
  

(from unrelated branch)

  $ hg log -r '_destmerge(foobranch)'
  abort: branch 'foobranch' has one head - please merge with an explicit rev
  (run 'hg heads' to see all heads)
  [255]