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)
a -> a not a symlink
% test replacing a file with a symlink
a -> b
popping symlink.patch
now at: base.patch
applying symlink.patch
now at: symlink.patch
a -> b
% test updating a symlink
a -> c
popping updatelink
now at: symlink.patch
applying updatelink
patching file a
a
now at: updatelink
a -> c
% test replacing a symlink with a file
popping replacelinkwithfile
now at: addlink
applying replacelinkwithfile
now at: replacelinkwithfile
sss
% test symlink removal
popping removesl.patch
now at: replacelinkwithfile
applying removesl.patch
now at: removesl.patch
C b
C c
C s