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)
changeset: 2:effea6de0384
tag: tip
parent: 0:bbd179dfa0a7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add bar
changeset: 1:ed1b79f46b9a
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: change foo
changeset: 0:bbd179dfa0a7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo
% pull a missing revision
abort: unknown revision 'missing'!
% pull multiple revisions with update
0:bbd179dfa0a7
rolling back to revision 0 (undo pull)
% pull -r 0
changeset: 0:bbd179dfa0a7
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo
% pull -r 1
changeset: 1:ed1b79f46b9a
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: change foo
changeset: 0:bbd179dfa0a7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo
% pull -r 1 again