[meld/deprecation-cleanup] meldbuffer: Move file-changed to Signal

[Kai Willadsen <kaiw src gnome org>]

commit 9ce12d048d813a5e6d9fa148f1f08f740634fcc0
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Dec 9 07:04:06 2018 +1000

    meldbuffer: Move file-changed to Signal
    
    Note that this is the buffer-specific file-changed signal, *not* the
    file-changed from MeldDoc. Naming is hard, okay?

 meld/filediff.py   | 2 +-
 meld/meldbuffer.py | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index ab2d3bf8..d091b638 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -178,7 +178,7 @@ class FileDiff(MeldDoc, Component):
             buf.undo_sequence = self.undosequence
             buf.connect("notify::has-selection",
                         self.update_text_actions_sensitivity)
-            buf.data.connect('file-changed', self.notify_file_changed)
+            buf.data.file_changed_signal.connect(self.notify_file_changed)
 
         self.ui_file = ui_file("filediff-ui.xml")
         self.actiongroup = self.FilediffActions
diff --git a/meld/meldbuffer.py b/meld/meldbuffer.py
index 35e8f4f9..fd95aa14 100644
--- a/meld/meldbuffer.py
+++ b/meld/meldbuffer.py
@@ -87,9 +87,9 @@ class MeldBuffer(GtkSource.Buffer):
 
 class MeldBufferData(GObject.GObject):
 
-    __gsignals__ = {
-        str('file-changed'): (GObject.SignalFlags.RUN_FIRST, None, ()),
-    }
+    @GObject.Signal('file-changed')
+    def file_changed_signal(self) -> None:
+        ...
 
     encoding = GObject.Property(
         type=GtkSource.Encoding,
@@ -160,7 +160,7 @@ class MeldBufferData(GObject.GObject):
     def _handle_file_change(self, monitor, f, other_file, event_type):
         mtime = self._query_mtime(f)
         if self._disk_mtime and mtime and mtime > self._disk_mtime:
-            self.emit('file-changed')
+            self.file_changed_signal.emit()
         self._disk_mtime = mtime or self._disk_mtime
 
     @property