store: optimize fncache._write by direncoding the contents in one go
For a netbeans clone on Windows 7 x64:
Before:
$ hg perffncachewrite
! wall 0.210000 comb 0.218401 user 0.202801 sys 0.015600 (best of 47)
After:
$ hg perffncachewrite
! wall 0.104000 comb 0.109201 user 0.078000 sys 0.031200 (best of 95)
hg debuginstall
$ hg debuginstall
checking encoding (ascii)...
checking Python lib (*lib*)... (glob)
checking installed modules (*mercurial)... (glob)
checking templates (*mercurial?templates)... (glob)
checking commit editor...
checking username...
no problems detected
hg debuginstall with no username
$ HGUSER= hg debuginstall
checking encoding (ascii)...
checking Python lib (*lib*)... (glob)
checking installed modules (*mercurial)... (glob)
checking templates (*mercurial?templates)... (glob)
checking commit editor...
checking username...
no username supplied (see "hg help config")
(specify a username in your configuration file)
1 problems detected, please check your install!
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