comparison tests/test-rebase-obsolete.t @ 33807:0975506120fb

rebase: rewrite core algorithm (issue5578) (issue5630)

"defineparents" is the core algorithm of rebase. The old code has too many
tech debts (like outdated comments, confusing assertions, etc) and is very
error-prone to be improved. This patch rewrites "defineparents" to make the
code easier to reason about, and solve a bunch of issues, including:

  - Assertion error: no base found (demonstrated by D212, issue5578)
  - Asymmetric result (demonstrated by D211, "F with one parent")
  - Wrong new parent (demonstrated by D262, "C':A'A'")
  - "revlog index out of range" (demonstrated by D262, issue5630)
  - "nothing to merge" (demonstrated by D262)

As a side effect, merge base decision has been made more solid - rebase now
prints out explicitly what could go wrong when it cannot find a unique
suitable merge base.

.. fix:: Issue 5578, Issue 5630

   Core rebase algorithm has been rewritten to be more robust.

Differential Revision: https://phab.mercurial-scm.org/D21

33806:f7d6978a4da9

  > B D G
  >  \|/
  >   A
  > EOF

BROKEN: This raises an exception
  $ hg rebase -d G -r 'B + D + F' 2>&1 | grep '^AssertionError'
  AssertionError: no base found to rebase on (defineparents called wrong)

  $ cd ..

test on rebase dropping a merge

  > E D B # replace: E -> B
  >  \|/
  >   A
  > EOF

BROKEN: Raises an exception
  $ hg rebase -d B -s E 2>&1 | grep AssertionError:
  AssertionError: no base found to rebase on (defineparents called wrong)
  $ hg log -G
  o    4:66f1a38021c9 F
  |\
  | x  3:7fb047a69f22 E
  | |
  o |  2:b18e25de2cf5 D
  |/
  | o  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  > EOF

  $ hg rebase -d C -s D
  note: not rebasing 2:b18e25de2cf5 "D" (D), already in destination as 1:112478962961 "B"
  rebasing 5:66f1a38021c9 "F" (F tip)
BROKEN: not rebased on top of requested destination (C)
  $ hg log -G
  o    6:50e9d60b99c6 F
  |\
  | | x  5:66f1a38021c9 F
  | |/|
  +-----o  4:26805aba1e60 C
  | | |
  | o |  3:7fb047a69f22 E
  | | |
  | | x  2:b18e25de2cf5 D
  | |/
  o |  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  > E D B # replace: E -> B
  >  \|/
  >   A
  > EOF

BROKEN: Raises an exception
  $ hg rebase -d C -s E 2>&1 | grep AssertionError:
  AssertionError: no base found to rebase on (defineparents called wrong)
  $ hg log -G
  o    5:66f1a38021c9 F
  |\
  | | o  4:26805aba1e60 C
  | | |
  | x |  3:7fb047a69f22 E
  | | |
  o | |  2:b18e25de2cf5 D
  |/ /
  | o  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  $ hg rebase -d C -b F
  rebasing 2:b18e25de2cf5 "D" (D)
  note: not rebasing 3:7fb047a69f22 "E" (E), already in destination as 1:112478962961 "B"
  rebasing 5:66f1a38021c9 "F" (F tip)
  $ hg log -G
  o  7:9ed45af61fa0 F
  |
  o  6:8f47515dda15 D
  |

  $ hg rebase -d C -b F
  note: not rebasing 2:b18e25de2cf5 "D" (D), already in destination as 1:112478962961 "B"
  rebasing 3:7fb047a69f22 "E" (E)
  rebasing 5:66f1a38021c9 "F" (F tip)
BROKEN: This should have resulted in a rebased F with one parent, just like in
the test case above
  $ hg log -G
  o    7:c1e6f26e339d F
  |\
  | o  6:533690786a86 E
  |/
  | x    5:66f1a38021c9 F
  | |\
  o | |  4:26805aba1e60 C
  | | |
  | | x  3:7fb047a69f22 E

33807:0975506120fb

  > B D G
  >  \|/
  >   A
  > EOF

  $ hg rebase -d G -r 'B + D + F'
  rebasing 1:112478962961 "B" (B)
  rebasing 2:b18e25de2cf5 "D" (D)
  not rebasing ignored 4:26805aba1e60 "C" (C)
  not rebasing ignored 5:4b61ff5c62e2 "E" (E)
  rebasing 6:f15c3adaf214 "F" (F tip)
  abort: cannot use revision 6 as base, result would have 3 parents
  [255]

  $ cd ..

test on rebase dropping a merge

  > E D B # replace: E -> B
  >  \|/
  >   A
  > EOF

  $ hg rebase -d B -s E
  note: not rebasing 3:7fb047a69f22 "E" (E), already in destination as 1:112478962961 "B"
  rebasing 4:66f1a38021c9 "F" (F tip)
  $ hg log -G
  o    5:aae1787dacee F
  |\
  | | x  4:66f1a38021c9 F
  | |/|
  | | x  3:7fb047a69f22 E
  | | |
  | o |  2:b18e25de2cf5 D
  | |/
  o /  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  > EOF

  $ hg rebase -d C -s D
  note: not rebasing 2:b18e25de2cf5 "D" (D), already in destination as 1:112478962961 "B"
  rebasing 5:66f1a38021c9 "F" (F tip)

  $ hg log -G
  o    6:0913febf6439 F
  |\
  +---x  5:66f1a38021c9 F
  | | |
  | o |  4:26805aba1e60 C
  | | |
  o | |  3:7fb047a69f22 E
  | | |
  +---x  2:b18e25de2cf5 D
  | |
  | o  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  > E D B # replace: E -> B
  >  \|/
  >   A
  > EOF

  $ hg rebase -d C -s E
  note: not rebasing 3:7fb047a69f22 "E" (E), already in destination as 1:112478962961 "B"
  rebasing 5:66f1a38021c9 "F" (F tip)
  $ hg log -G
  o    6:c6ab0cc6d220 F
  |\
  +---x  5:66f1a38021c9 F
  | | |
  | o |  4:26805aba1e60 C
  | | |
  | | x  3:7fb047a69f22 E
  | | |
  o---+  2:b18e25de2cf5 D
   / /
  o /  1:112478962961 B
  |/
  o  0:426bada5c675 A
  
  $ cd ..

  $ hg rebase -d C -b F
  rebasing 2:b18e25de2cf5 "D" (D)
  note: not rebasing 3:7fb047a69f22 "E" (E), already in destination as 1:112478962961 "B"
  rebasing 5:66f1a38021c9 "F" (F tip)
  warning: rebasing 5:66f1a38021c9 may include unwanted changes from 3:7fb047a69f22
  $ hg log -G
  o  7:9ed45af61fa0 F
  |
  o  6:8f47515dda15 D
  |

  $ hg rebase -d C -b F
  note: not rebasing 2:b18e25de2cf5 "D" (D), already in destination as 1:112478962961 "B"
  rebasing 3:7fb047a69f22 "E" (E)
  rebasing 5:66f1a38021c9 "F" (F tip)
  warning: rebasing 5:66f1a38021c9 may include unwanted changes from 2:b18e25de2cf5

  $ hg log -G
  o  7:502540f44880 F
  |
  o  6:533690786a86 E
  |
  | x    5:66f1a38021c9 F
  | |\
  o | |  4:26805aba1e60 C
  | | |
  | | x  3:7fb047a69f22 E