tests/test-bad-pull.t

revlog: move file writing to a separate function

Moves the code that actually writes to a file to a separate function in
revlog.py. This allows extensions to intercept and use the data being written to
disk. For example, an extension might want to replicate these writes elsewhere.

When cloning the Mercurial repo on /dev/shm with --pull, I see about a 0.3% perf change.
It goes from 28.2 to 28.3 seconds.

  $ "$TESTDIR/hghave" serve || exit 80

#if windows
  $ hg clone http://localhost:$HGPORT/ copy
  abort: * (glob)
  [255]
#else
  $ hg clone http://localhost:$HGPORT/ copy
  abort: error: Connection refused
  [255]
#endif

  $ test -d copy
  [1]

  $ cat > dumb.py <<EOF
  > import BaseHTTPServer, SimpleHTTPServer, os, signal
  > def run(server_class=BaseHTTPServer.HTTPServer,
  >         handler_class=SimpleHTTPServer.SimpleHTTPRequestHandler):
  >     server_address = ('localhost', int(os.environ['HGPORT']))
  >     httpd = server_class(server_address, handler_class)
  >     open("listening", "w")
  >     httpd.handle_request()
  > run()
  > EOF

  $ python dumb.py 2> log &
  $ P=$!
  $ while [ ! -f listening ]; do sleep 0; done
  $ hg clone http://localhost:$HGPORT/foo copy2
  abort: HTTP Error 404: * (glob)
  [255]
  $ wait $P