support for command documentation:

- made package tree handler generic so it can work on any fs tree
- cleanups along the way

R=rsc
CC=r
http://go/go-review/1017020

lib/godoc/dirs.html

@@ -1,5 +1,5 @@
 <table class="layout">
-<tr><td colspan="2"><a href="/pkg/{Path|html}">{Name|html}</a></td></tr>
+<tr><td colspan="2"><a href="{Path|path}">{Name|html}</a></td></tr>
 {.repeated section Dirs}
 	<tr><td width="25em"></td><td>{@|dir}</td></tr>
 {.end}

lib/godoc/godoc.html

@@ -44,6 +44,7 @@
 
     <li class="blank">&nbsp;</li>
     <li class="navhead">Programming</li>
+    <li><a href="/cmd" class="noline">Command documentation</a></li>
     <li><a href="/pkg" class="noline">Package documentation</a></li>
 
     <li class="blank">&nbsp;</li>

lib/godoc/package.html

@@ -6,17 +6,21 @@
 
 {.section PDoc}
 	<!-- PackageName is printed as title by the top-level template -->
-	<p><code>import "{ImportPath|html}"</code></p>
+	{.section IsPkg}
+		<p><code>import "{ImportPath|html}"</code></p>
+	{.end}
 	{Doc|html-comment}
-	{.section Filenames}
-		<p>
-		<h4>Package files</h4>
-		<span style="font-size:90%">
-		{.repeated section @}
-			<a href="/{FilePath|html}/{@|html}">{@|html}</a>
+	{.section IsPkg}
+		{.section Filenames}
+			<p>
+			<h4>Package files</h4>
+			<span style="font-size:90%">
+			{.repeated section @}
+				<a href="/{FilePath|html}/{@|html}">{@|html}</a>
+			{.end}
+			</span>
+			</p>
 		{.end}
-		</span>
-		</p>
 	{.end}
 	{.section Consts}
 		<h2>Constants</h2>

lib/godoc/package.txt

@@ -1,8 +1,12 @@
 {.section PDoc}
+{.section IsPkg}
 PACKAGE
 
 package {PackageName}
 import "{ImportPath}"
+{.or}
+COMMAND DOCUMENTATION
+{.end}
 {.section Doc}
 
 {@}