tests/test-convert-p4.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)

% create p4 depot
% start the p4 server
% create a client spec
Client hg-p4-import saved.
% populate the depot
//depot/test-mercurial-import/a#1 - opened for add
//depot/test-mercurial-import/b/c#1 - opened for add
Submitting change 1.
Locking 2 files ...
add //depot/test-mercurial-import/a#1
add //depot/test-mercurial-import/b/c#1
Change 1 submitted.
% change some files
//depot/test-mercurial-import/a#1 - opened for edit
Submitting change 2.
Locking 1 files ...
edit //depot/test-mercurial-import/a#2
Change 2 submitted.
//depot/test-mercurial-import/b/c#1 - opened for edit
Submitting change 3.
Locking 1 files ...
edit //depot/test-mercurial-import/b/c#2
Change 3 submitted.
% convert
initializing destination dst repository
reading p4 views
collecting p4 changelists
1 initial
2 change a
3 change b/c
scanning source...
sorting...
converting...
2 initial
1 change a
0 change b/c
rev=2 desc="change b/c" tags="tip" files="b/c"
rev=1 desc="change a" tags="" files="a"
rev=0 desc="initial" tags="" files="a b/c"
% change some files
//depot/test-mercurial-import/a#2 - opened for edit
//depot/test-mercurial-import/b/c#2 - opened for edit
Submitting change 4.
Locking 2 files ...
edit //depot/test-mercurial-import/a#3
edit //depot/test-mercurial-import/b/c#3
Change 4 submitted.
% convert again
reading p4 views
collecting p4 changelists
1 initial
2 change a
3 change b/c
4 change a b/c
scanning source...
sorting...
converting...
0 change a b/c
rev=3 desc="change a b/c" tags="tip" files="a b/c"
rev=2 desc="change b/c" tags="" files="b/c"
rev=1 desc="change a" tags="" files="a"
rev=0 desc="initial" tags="" files="a b/c"
% interesting names
//depot/test-mercurial-import/d d#1 - opened for add
//depot/test-mercurial-import/ e/ f#1 - opened for add
Submitting change 5.
Locking 2 files ...
add //depot/test-mercurial-import/ e/ f#1
add //depot/test-mercurial-import/d d#1
Change 5 submitted.
% convert again
reading p4 views
collecting p4 changelists
1 initial
2 change a
3 change b/c
4 change a b/c
5 add d e f
scanning source...
sorting...
converting...
0 add d e f
rev=4 desc="add d e f" tags="tip" files=" e/ f d d"
rev=3 desc="change a b/c" tags="" files="a b/c"
rev=2 desc="change b/c" tags="" files="b/c"
rev=1 desc="change a" tags="" files="a"
rev=0 desc="initial" tags="" files="a b/c"
% stop the p4 server