Instead of serving files of the underlying OS file system,
a .zip file may be provided to godoc containing the files
to serve; for instance:
godoc -http=:6060 -zip=go.zip
using a .zip file created from a clean tree as follows:
zip -r go.zip $GOROOT
R=rsc
CC=golang-dev
https://golang.org/cl/4670053
of accesses via a FileSystem interface.
Preparation for appengine version which gets its files
via a snapshot or zip file and uses a corresponding
FileSystem implementation.
R=rsc, r
CC=golang-dev
https://golang.org/cl/4572065