publisher: restore SourceRoot configurability

This change allows the publisher to use resources from a SourceRoot
directory, without having to rebuild the publisher binary, instead of
only using embedded resources.

Change-Id: Ife29e3015b8595a33f175a62d98fcf5ffa689134

app/publisher/main.go

@@ -142,13 +142,12 @@ func newPublishHandler(conf *config) *publishHandler {
 	}
 	var CSSFiles, JSDeps []string
 	if conf.SourceRoot != "" {
-		appRoot := filepath.Join(conf.SourceRoot, "app", "publisher")
 		Files = &fileembed.Files{
-			DirFallback: appRoot,
+			DirFallback: conf.SourceRoot,
 		}
 		// TODO(mpl): Can I readdir by listing with "/" on Files, even with DirFallBack?
 		// Apparently not, but retry later.
-		dir, err := os.Open(appRoot)
+		dir, err := os.Open(conf.SourceRoot)
 		if err != nil {
 			logger.Fatal(err)
 		}

pkg/serverinit/genconfig.go

@@ -152,6 +152,9 @@ func (b *lowBuilder) addPublishedConfig(tlsO *tlsOpts) error {
 			"cacheRoot":  v.CacheRoot,
 			"goTemplate": v.GoTemplate,
 		}
+		if v.SourceRoot != "" {
+			appConfig["sourceRoot"] = v.SourceRoot
+		}
 		if v.HTTPSCert != "" && v.HTTPSKey != "" {
 			// user can specify these directly in the publish section
 			appConfig["httpsCert"] = v.HTTPSCert

pkg/types/serverconfig/config.go

@@ -134,6 +134,12 @@ type Publish struct {
 	// caching blobserver (for images). No caching if empty.
 	// An example value is Config.BlobPath + "/cache".
 	CacheRoot string `json:"cacheRoot,omitempty"`
+
+	// SourceRoot optionally defines the directory where to look for some resources
+	// such as HTML templates, as well as javascript, and CSS files. The
+	// default is to use the resources embedded in the publisher binary, found
+	// in the publisher app source directory.
+	SourceRoot string `json:"sourceRoot,omitempty"`
 }
 
 // invertedBool is a bool that marshals to and from JSON with the opposite of its in-memory value.