it used to cache open files. this made revlogng break because it wants
to rename files when splitting .i into .i/.d, but cannot rename or unlink
open files on windows.
new code is bit slower, but safe on linux and windows. proper fix for
too many open/close of changelog/manifest belongs in different place.
can get 10% speed improvement back.
The appendfile code was not passing default version info to the
changelog or manifest classes, and so they were always being created
as version 0.
revlog.checkinlinesize had to be corrected to seek to the end
of the index file when no index file was passed (only clone does this)
The appendfile class needs a few changes to make it work with interleaved
index files. It needs to support the tell() method, opening in a+ mode,
and it needs to delay the checkinlinesize call until after the
append file is written.
Given that open(file, "a+") doesn't always seek to the end of the file,
this adds seek operations to appendfile that understand whence args
write to file opened mode 'a+' should write to end of file and update
offset pointer, but does not (solaris 10 has python 2.3.3).
fix is to always seek.
