Enable soft livereload of CSS and images

Prior to this commit a dummy JavaScript filename was sent to LiveReload when changing a static file (CSS, image etc.), forcing a full browser reload of the page.

This commit fixes this by sending the relative file path of the changed static resource, enabling partial live reloading for CSS- and image-changes. If more than one static file happens to end up in the same changeevent-batch, it will fall back to do a full refresh. To enable this logic, the change events with names ending with ".goutputstream*" is now filtered out as temporary.

Changes in dynamic content behaves like before.

Issue #490

helpers/path.go

@@ -14,6 +14,7 @@
 package helpers
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -130,6 +131,23 @@ func AbsPathify(inPath string) string {
 	return filepath.Clean(filepath.Join(viper.GetString("WorkingDir"), inPath))
 }
 
+func MakeStaticPathRelative(inPath string) (string, error) {
+	staticDir := AbsPathify(viper.GetString("StaticDir"))
+	themeStaticDir := AbsPathify("themes/"+viper.GetString("theme")) + "/static/"
+
+	return MakePathRelative(inPath, staticDir, themeStaticDir)
+}
+
+func MakePathRelative(inPath string, possibleDirectories ...string) (string, error) {
+
+	for _, currentPath := range possibleDirectories {
+		if strings.HasPrefix(inPath, currentPath) {
+			return strings.TrimPrefix(inPath, currentPath), nil
+		}
+	}
+	return inPath, errors.New("Can't extract relative path, unknown prefix")
+}
+
 func Filename(in string) (name string) {
 	name, _ = FileAndExt(in)
 	return