godoc: provide mode for flat (non-indented) directory listings

This feature should make it easier to look at very large
directory trees.

- a new mode (URL: /pkg/?m=flat) shows directory listings w/o
  indentation and entries with full path (html and text mode)
- in text mode, hierarchical (non-flat) directory listings are
  now presented with indentation (/pkg/?m=text)
- in html mode, hierarchical (non-flat) directory listings are
  presented with slightly less indentation
- there is an internal hook for programmatic control of the
  display mode (for specialized versions of godoc).

R=bradfitz
CC=golang-dev, rsc
https://golang.org/cl/5410043

lib/godoc/package.html

@@ -141,17 +141,25 @@
 	<p>
 	<table class="layout">
 	<tr>
+	{{if $.DirFlat}}
+		<th align="left">Name</th>
+	{{else}}
 		<th align="left" colspan="{{html .MaxHeight}}">Name</th>
-	<td width="25">&nbsp;</td>
+	{{end}}
+	<th width="25"></th>
 	<th align="left">Synopsis</th>
 	</tr>
 	<tr>
-	<th align="left"><a href="..">..</a></th>
+	<td align="left"><a href="..">..</a></td>
 	</tr>
 	{{range .List}}
 		<tr>
-		{{repeat `<td width="25"></td>` .Depth}}
+		{{if $.DirFlat}}
+			<td align="left"><a href="{{html .Path}}">{{html .Path}}</a></td>
+		{{else}}
+			{{repeat `<td width="20"></td>` .Depth}}
 			<td align="left" colspan="{{html .Height}}"><a href="{{html .Path}}">{{html .Name}}</a></td>
+		{{end}}
 		<td></td>
 		<td align="left">{{html .Synopsis}}</td>
 		</tr>

lib/godoc/package.txt

@@ -76,7 +76,8 @@ OTHER PACKAGES
 
 */}}{{with .Dirs}}
 SUBDIRECTORIES
-
-{{range .List}}
-	{{.Name}}{{end}}
-{{end}}
+{{if $.DirFlat}}{{range .List}}
+	{{.Path}}{{end}}
+{{else}}{{range .List}}
+	{{repeat `. ` .Depth}}{{.Name}}{{end}}
+{{end}}{{end}}

src/cmd/godoc/doc.go

@@ -134,10 +134,11 @@ The presentation mode of web pages served by godoc can be controlled with the
 	all	show documentation for all (not just exported) declarations
 	src	show the original source code rather then the extracted documentation
 	text	present the page in textual (command-line) form rather than HTML
+	flat	present flat (not indented) directory listings using full paths
 
-For instance, http://golang.org/pkg/big/?m=all,text shows the documentation for
-all (not just the exported) declarations of package big, in textual form (as
-it would appear when using godoc from the command line: "godoc -src big .*").
+For instance, http://golang.org/pkg/math/big/?m=all,text shows the documentation
+for all (not just the exported) declarations of package big, in textual form (as
+it would appear when using godoc from the command line: "godoc -src math/big .*").
 
 By default, godoc serves files from the file system of the underlying OS.
 Instead, a .zip file may be provided via the -zip flag, which contains

src/cmd/godoc/godoc.go

@@ -825,6 +825,7 @@ const (
 	noFiltering PageInfoMode = 1 << iota // do not filter exports
 	showSource                           // show source code, do not extract documentation
 	noHtml                               // show result in textual form, do not generate HTML
+	flatDir                              // show directory in a flat (non-indented) manner
 )
 
 // modeNames defines names for each PageInfoMode flag.
@@ -832,18 +833,26 @@ var modeNames = map[string]PageInfoMode{
 	"all":  noFiltering,
 	"src":  showSource,
 	"text": noHtml,
+	"flat": flatDir,
 }
 
 // getPageInfoMode computes the PageInfoMode flags by analyzing the request
 // URL form value "m". It is value is a comma-separated list of mode names
 // as defined by modeNames (e.g.: m=src,text).
-func getPageInfoMode(r *http.Request) (mode PageInfoMode) {
+func getPageInfoMode(r *http.Request) PageInfoMode {
+	var mode PageInfoMode
 	for _, k := range strings.Split(r.FormValue("m"), ",") {
 		if m, found := modeNames[strings.TrimSpace(k)]; found {
 			mode |= m
 		}
 	}
-	return
+	return adjustPageInfoMode(r, mode)
+}
+
+// Specialized versions of godoc may adjust the PageInfoMode by overriding
+// this variable.
+var adjustPageInfoMode = func(_ *http.Request, mode PageInfoMode) PageInfoMode {
+	return mode
 }
 
 // remoteSearchURL returns the search URL for a given query as needed by
@@ -868,8 +877,9 @@ type PageInfo struct {
 	Examples []*doc.Example  // nil if no example code
 	Dirs     *DirList        // nil if no directory information
 	DirTime  int64           // directory time stamp in seconds since epoch
+	DirFlat  bool            // if set, show directory in a flat (non-indented) manner
 	IsPkg    bool            // false if this is not documenting a real package
-	Err      error           // directory read error or nil
+	Err      error           // I/O error or nil
 }
 
 func (info *PageInfo) IsEmpty() bool {
@@ -1105,7 +1115,19 @@ func (h *httpHandler) getPageInfo(abspath, relpath, pkgname string, mode PageInf
 		timestamp = time.Seconds()
 	}
 
-	return PageInfo{abspath, plist, fset, past, pdoc, examples, dir.listing(true), timestamp, h.isPkg, nil}
+	return PageInfo{
+		Dirname:  abspath,
+		PList:    plist,
+		FSet:     fset,
+		PAst:     past,
+		PDoc:     pdoc,
+		Examples: examples,
+		Dirs:     dir.listing(true),
+		DirTime:  timestamp,
+		DirFlat:  mode&flatDir != 0,
+		IsPkg:    h.isPkg,
+		Err:      nil,
+	}
 }
 
 func (h *httpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {