Remove all of the code generation and the concept of "APPDIR" - just
generate godoc.zip and index files in the app directory.
Simplify generation of the zip - use a symlink so that every file in
godoc.zip is under the "goroot" directory, regardless of the
environment. Previously, the prefix would be dependent on the location
of the user's GOROOT.
Running the setup script is now optional - it's now possible to run
dev_appserver.py on a regular checkout of cmd/godoc without godoc.zip
and search index files. Use environment variables to switch whether the
zip file is used vs reading GOROOT from the filesystem.
Change-Id: I1ce95c891717fe2da975f979778fd775b23f18c8
Reviewed-on: https://go-review.googlesource.com/46725
Reviewed-by: Andrew Bonventre <andybons@golang.org>
