[meld] Prompt for a filename when saving read-only files, rather than complain

[Kai Willadsen <kaiw src gnome org>]

commit 86c8e03402bba90d51f0502f89c82e2c5b2841da
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Mon Dec 24 09:27:52 2012 +1000

    Prompt for a filename when saving read-only files, rather than complain

 meld/filediff.py |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index f3334a3..a79099b 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -1396,11 +1396,12 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
     def save_file(self, pane, saveas=0):
         buf = self.textbuffer[pane]
         bufdata = buf.data
-        if saveas or not bufdata.filename:
-            filename = self._get_filename_for_saving( _("Choose a name for buffer %i.") % (pane+1) )
+        if saveas or not bufdata.filename or not bufdata.writable:
+            prompt = _("Choose a name for buffer %i.") % (pane + 1)
+            filename = self._get_filename_for_saving(prompt)
             if filename:
                 bufdata.filename = bufdata.label = os.path.abspath(filename)
-                self.fileentry[pane].set_filename( bufdata.filename)
+                self.fileentry[pane].set_filename(bufdata.filename)
                 self.fileentry[pane].prepend_history(bufdata.filename)
             else:
                 return False