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)
adding a
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
created new head
searching for copies back to rev 1
resolving manifests
overwrite None partial False
ancestor c334dc3be0da local 521a1e40188f+ remote 3574f3e69b1c
conflicting flags for a
(n)one, e(x)ec or sym(l)ink? n
a: update permissions -> e
update: a 1/1 files (100.00%)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% symlink is local parent, executable is other
a has no flags (default for conflicts)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
searching for copies back to rev 1
resolving manifests
overwrite None partial False
ancestor c334dc3be0da local 3574f3e69b1c+ remote 521a1e40188f
conflicting flags for a
(n)one, e(x)ec or sym(l)ink? n
a: remote is newer -> g
update: a 1/1 files (100.00%)
getting a
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% symlink is other parent, executable is local
a has no flags (default for conflicts)