Factor Mime Type guessing into fs.MimeType()

fs/operations.go

@@ -5,6 +5,8 @@ package fs
 import (
 	"fmt"
 	"io"
+	"mime"
+	"path"
 	"sync"
 )
 
@@ -97,6 +99,15 @@ func Equal(src, dst Object) bool {
 	return true
 }
 
+// Returns a guess at the mime type from the extension
+func MimeType(o Object) string {
+	mimeType := mime.TypeByExtension(path.Ext(o.Remote()))
+	if mimeType == "" {
+		mimeType = "application/octet-stream"
+	}
+	return mimeType
+}
+
 // Used to remove a failed copy
 func removeFailedCopy(dst Object) {
 	if dst != nil {