tests/test-double-merge.out

findrenames: Optimise "addremove -s100" by matching files by their SHA1 hashes.

We speed up 'findrenames' for the usecase when a user specifies they
want a similarity of 100% by matching files by their exact SHA1 hash
value. This reduces the number of comparisons required to find exact
matches from O(n^2) to O(n).

While it would be nice if we could just use mercurial's pre-calculated
SHA1 hash for existing files, this hash includes the file's ancestor
information making it unsuitable for our purposes. Instead, we calculate
the hash of old content from scratch.

The following benchmarks were taken on the current head of crew:

addremove 100% similarity:
  rm -rf *; hg up -C; mv tests tests.new
  hg --time addremove -s100 --dry-run

  before:  real 176.350 secs (user 128.890+0.000 sys 47.430+0.000)
  after:   real   2.130 secs (user   1.890+0.000 sys  0.240+0.000)

addremove 75% similarity:
  rm -rf *; hg up -C; mv tests tests.new; \
      for i in tests.new/*; do echo x >> $i; done
  hg --time addremove -s75  --dry-run

  before: real 264.560 secs (user 215.130+0.000 sys 49.410+0.000)
  after:  real 218.710 secs (user 172.790+0.000 sys 45.870+0.000)

created new head
changeset:   1:d9da848d0adf
user:        test
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     cp foo bar; change both

  searching for copies back to rev 1
  unmatched files in other:
   bar
  all copies found (* = to merge, ! = divergent):
   bar -> foo *
  checking for directory renames
resolving manifests
 overwrite None partial False
 ancestor 310fd17130da local 2092631ce82b+ remote d9da848d0adf
 foo: versions differ -> m
 foo: remote copied to bar -> m
preserving foo for resolve of bar
preserving foo for resolve of foo
update: foo 1/2 files (50.00%)
picked tool 'internal:merge' for bar (binary False symlink False)
merging foo and bar to bar
my bar@2092631ce82b+ other bar@d9da848d0adf ancestor foo@310fd17130da
 premerge successful
update: foo 2/2 files (100.00%)
picked tool 'internal:merge' for foo (binary False symlink False)
merging foo
my foo@2092631ce82b+ other foo@d9da848d0adf ancestor foo@310fd17130da
 premerge successful
0 files updated, 2 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
-- foo --
line 0
line 1
line 2-1
-- bar --
line 0
line 1
line 2-2