branches: improve performance by removing redundant operations This refactors the branches command so it collects all the information it needs about a branch in one pass over the branch map. In particular, it fixes an issue where the command called repo.branchtags() to get branch tips, and then used repo.branchheads() to get the closed/open status. Both repo methods read the changelog to determine if the branch is closed, resulting in extra, redundant I/O. For the PyPy repo with 744 branches and 843 branch heads, this brings hg branches over NFS from: CallCount Recursive Total(ms) Inline(ms) module:lineno(function) 2427 0 0.9057 0.9057 <open> 2424 0 0.4096 0.4096 <method 'close' of 'file' objects> 2424 0 0.0476 0.0476 <method 'read' of 'file' objects> 1 0 0.0468 0.0468 mercurial.revlog:637(headrevs) +1 0 0.0000 0.0000 +<len> 2422 0 0.0443 0.0443 <method 'seek' of 'file' objects> 2962 0 0.0337 0.0337 <zlib.decompress> 2491 0 1.8008 0.0322 mercurial.changelog:182(read) +2491 0 1.6982 0.0315 +mercurial.revlog:881(revision) +2488 0 0.0269 0.0134 +mercurial.changelog:28(decodeextra) +4982 0 0.0085 0.0085 +<method 'split' of 'str' objects> +4982 0 0.0274 0.0049 +mercurial.encoding:61(tolocal) +2491 0 0.0039 0.0039 +<method 'index' of 'str' objects> 2491 0 1.6982 0.0315 mercurial.revlog:881(revision) +2413 0 0.0112 0.0112 +mercurial.revlog:305(rev) +2491 0 1.5315 0.0068 +mercurial.revlog:847(_chunkraw) +2491 0 0.0414 0.0058 +mercurial.revlog:945(_checkhash) +2491 0 0.0028 0.0028 +mercurial.revlog:349(flags) +2491 0 0.0025 0.0025 +<mercurial.mpatch.patches> 2422 0 1.5089 0.0286 mercurial.revlog:818(_loadchunk) +2422 0 0.4093 0.4093 +<method 'close' of 'file' objects> +2422 0 0.0451 0.0451 +<method 'read' of 'file' objects> +2422 0 0.0443 0.0443 +<method 'seek' of 'file' objects> +2422 0 0.9703 0.0096 +mercurial.store:374(__call__) +2422 0 0.0079 0.0069 +mercurial.revlog:810(_addchunk) 5804 0 0.0204 0.0204 mercurial.revlog:305(rev) 2426 0 0.9552 0.0177 mercurial.scmutil:218(__call__) +2426 0 0.9057 0.9057 +<open> +2426 0 0.0120 0.0083 +os.path:80(split) +2426 0 0.0061 0.0049 +mercurial.scmutil:92(__call__) Time: real 1.950 secs (user 0.560+0.000 sys 0.220+0.000) down to: CallCount Recursive Total(ms) Inline(ms) module:lineno(function) 1545 0 0.6035 0.6035 <open> 1542 0 0.2697 0.2697 <method 'close' of 'file' objects> 1 0 0.0547 0.0547 mercurial.revlog:637(headrevs) +1 0 0.0000 0.0000 +<len> 1542 0 0.0389 0.0389 <method 'read' of 'file' objects> 1540 0 0.0316 0.0316 <method 'seek' of 'file' objects> 1853 0 0.0227 0.0227 <zlib.decompress> 1557 0 1.2131 0.0226 mercurial.changelog:182(read) +1557 0 1.1398 0.0221 +mercurial.revlog:881(revision) +1555 0 0.0199 0.0094 +mercurial.changelog:28(decodeextra) +3114 0 0.0058 0.0058 +<method 'split' of 'str' objects> +3114 0 0.0196 0.0035 +mercurial.encoding:61(tolocal) +1557 0 0.0026 0.0026 +<method 'index' of 'str' objects> 1557 0 1.1398 0.0221 mercurial.revlog:881(revision) +1557 0 1.0307 0.0047 +mercurial.revlog:847(_chunkraw) +1557 0 0.0287 0.0040 +mercurial.revlog:945(_checkhash) +1557 0 0.0018 0.0018 +<mercurial.mpatch.patches> +1557 0 0.0018 0.0018 +mercurial.revlog:326(node) +1557 0 0.0417 0.0013 +mercurial.revlog:857(_chunkbase) 1540 0 1.0147 0.0210 mercurial.revlog:818(_loadchunk) +1540 0 0.2693 0.2693 +<method 'close' of 'file' objects> +1540 0 0.0360 0.0360 +<method 'read' of 'file' objects> +1540 0 0.0316 0.0316 +<method 'seek' of 'file' objects> +1540 0 0.6487 0.0070 +mercurial.store:374(__call__) +1540 0 0.0059 0.0052 +mercurial.revlog:810(_addchunk) 3192 0 0.0173 0.0173 mercurial.revlog:305(rev) 8184 0 0.0300 0.0147 <method 'decode' of 'str' objects> +5204 0 0.0149 0.0048 +encodings.utf_8:15(decode) +1 0 0.0004 0.0000 +encodings:71(search_function) 43 26 0.0147 0.0129 <__import__> Time: real 1.390 secs (user 0.450+0.000 sys 0.170+0.000)