tests/test-addremove-similar.t

bdiff: balance recursion to avoid quadratic behavior (issue4704)

For highly structured files like JSON or XML dumps with large numbers
of duplicate lines (eg braces) and isolated matching lines, bdiff
could find large numbers of equally good spans. Because it prefers
earlier matches, this would result in pathologically unbalance
recursion that resulted in quadratic performance.

This patch makes it prefer matches closer to the middle that tend to
balance recursion. This change improves the speed of a pathological
test case from 1100s to 9s.

Included is a smaller test that has a roughly 50x safety margin on the
performance it accepts. It's likely to fail on pure builds because
difflib also has a recursion-balancing problem.

  $ hg init rep; cd rep

  $ touch empty-file
  $ $PYTHON -c 'for x in range(10000): print x' > large-file

  $ hg addremove
  adding empty-file
  adding large-file

  $ hg commit -m A

  $ rm large-file empty-file
  $ $PYTHON -c 'for x in range(10,10000): print x' > another-file

  $ hg addremove -s50
  adding another-file
  removing empty-file
  removing large-file
  recording removal of large-file as rename to another-file (99% similar)

  $ hg commit -m B

comparing two empty files caused ZeroDivisionError in the past

  $ hg update -C 0
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ rm empty-file
  $ touch another-empty-file
  $ hg addremove -s50
  adding another-empty-file
  removing empty-file

  $ cd ..

  $ hg init rep2; cd rep2

  $ $PYTHON -c 'for x in range(10000): print x' > large-file
  $ $PYTHON -c 'for x in range(50): print x' > tiny-file

  $ hg addremove
  adding large-file
  adding tiny-file

  $ hg commit -m A

  $ $PYTHON -c 'for x in range(70): print x' > small-file
  $ rm tiny-file
  $ rm large-file

  $ hg addremove -s50
  removing large-file
  adding small-file
  removing tiny-file
  recording removal of tiny-file as rename to small-file (82% similar)

  $ hg commit -m B

should all fail

  $ hg addremove -s foo
  abort: similarity must be a number
  [255]
  $ hg addremove -s -1
  abort: similarity must be between 0 and 100
  [255]
  $ hg addremove -s 1e6
  abort: similarity must be between 0 and 100
  [255]

  $ cd ..

Issue1527: repeated addremove causes Abort

  $ hg init rep3; cd rep3
  $ mkdir d
  $ echo a > d/a
  $ hg add d/a
  $ hg commit -m 1

  $ mv d/a d/b
  $ hg addremove -s80
  removing d/a
  adding d/b
  recording removal of d/a as rename to d/b (100% similar) (glob)
  $ hg debugstate
  r   0          0 1970-01-01 00:00:00 d/a
  a   0         -1 unset               d/b
  copy: d/a -> d/b
  $ mv d/b c

no copies found here (since the target isn't in d

  $ hg addremove -s80 d
  removing d/b (glob)

copies here

  $ hg addremove -s80
  adding c
  recording removal of d/a as rename to c (100% similar) (glob)

  $ cd ..