view tests/test-merge6.t @ 30441:3633403888ae

bdiff: give slight preference to appending lines

[This change could be folded into the previous changeset to minimize the repo
churn ...]

The general preference to matches in the middle of bdiff ranges helps getting
balanced recursion and efficient computation. But, as previous changes have
shown, it might also give diffs that seems "obviously wrong".

To mitigate that: If the best match on the A side starts at the beginning of
the bdiff range, don't aim for the middle-most B side match but for the
earliest.

This will make the matches balanced (by both sides being "early") even though
the bisection will be less balanced. Still, this case only apply if the *best*
and middle-most match was fully unbalanced on the A side. Each recursion will
thus even in this worst case reduce the problem significantly and we are not
re-introducing the problem that was fixed in f1ca249696ed.

The bundle size for 4.0 (hg bundle --base null -r 4.0 x.hg) happens to go from
22806817 to 22807275 bytes - a 0.002% increase.

This make the recent test-bdiff.py changes give a more pretty output ... but
they no longer show that the recursion is around middle matches (because it in
these cases isn't).

  $ cat <<EOF > merge
  > import sys, os
  > print "merging for", os.path.basename(sys.argv[1])
  > EOF
  $ HGMERGE="python ../merge"; export HGMERGE

  $ hg init A1
  $ cd A1
  $ echo This is file foo1 > foo
  $ echo This is file bar1 > bar
  $ hg add foo bar
  $ hg commit -m "commit text"

  $ cd ..
  $ hg clone A1 B1
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd A1
  $ rm bar
  $ hg remove bar
  $ hg commit -m "commit test"

  $ cd ../B1
  $ echo This is file foo22 > foo
  $ hg commit -m "commit test"

  $ cd ..
  $ hg clone A1 A2
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg clone B1 B2
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd A1
  $ hg pull ../B1
  pulling from ../B1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "commit test"
bar should remain deleted.
  $ hg manifest --debug
  f9b0e817f6a48de3564c6b2957687c5e7297c5a0 644   foo

  $ cd ../B2
  $ hg pull ../A2
  pulling from ../A2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg merge
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "commit test"
bar should remain deleted.
  $ hg manifest --debug
  f9b0e817f6a48de3564c6b2957687c5e7297c5a0 644   foo

  $ cd ..