godoc: basic setup for running godoc on local app engine emulator

R=rsc
CC=golang-dev
https://golang.org/cl/4559058

misc/godoc/README

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+Instructions to get an initial godoc running on a local app engine emulator
+---------------------------------------------------------------------------
+
+To run godoc under the app engine emulator, create a ("goroot") godoc
+directory that contains the app.yaml file, the doc and lib directories
+from the Go distribution, as well as a godoc directory with the godoc
+sources from src/cmd/godoc. In the godoc source directory, replace
+main.go with init.go. The directory structure should look as follows:
+
+godoc				// "goroot" directory
+	app.yaml		// app engine control file
+	doc			// goroot/doc directory
+	favicon.ico
+	godoc			// contains godoc sources
+		godoc.go	// unchanged godoc file
+		init.go		// this file instead of godoc/main.go
+		...		// remaining godoc files
+	lib			// goroot/lib directory
+
+Run app engine emulator locally: dev_appserver.py -a <hostname> godoc
+where godoc is the top-level "goroot" directory. The godoc home page
+is then served at: <hostname>:8080 .

misc/godoc/app.yaml

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+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+application: godoc
+version: 1
+runtime: go
+api_version: 1
+
+handlers:
+- url: /.*
+  script: _go_app

misc/godoc/init.go

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+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file replaces main.go when running godoc under the app engine emulator.
+// See the README file for instructions.
+
+package main
+
+import (
+	"http"
+	"log"
+	"os"
+	"path/filepath"
+)
+
+func serveError(w http.ResponseWriter, r *http.Request, relpath string, err os.Error) {
+	contents := applyTemplate(errorHTML, "errorHTML", err) // err may contain an absolute path!
+	w.WriteHeader(http.StatusNotFound)
+	servePage(w, "File "+relpath, "", "", contents)
+}
+
+func init() {
+	// set goroot
+	cwd, err := os.Getwd()
+	if err != nil {
+		log.Fatalf("cwd: %s", err)
+	}
+	log.Printf("cwd = %s", cwd)
+	*goroot = filepath.Clean(cwd)
+
+	initHandlers()
+	readTemplates()
+	registerPublicHandlers(http.DefaultServeMux)
+}