[gnome-builder/gnome-builder-3-28] bufmgr: avoid re-saving file to disk when possible

[Christian Hergert <chergert src gnome org>]

commit e18d0ce83aa3e63777142fcdcbe8cb790445071a
Author: Christian Hergert <chergert redhat com>
Date:   Tue Mar 20 15:17:24 2018 -0700

    bufmgr: avoid re-saving file to disk when possible
    
    This helps avoid a changed on disk notification from the file monitor as
    well as needlessly rewriting the same data back.
    
    Since tooling such as plugins can cause these files to be saved, we want
    to protect ourselves against them doing so needlessly.

 src/libide/buffers/ide-buffer-manager.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
---
diff --git a/src/libide/buffers/ide-buffer-manager.c b/src/libide/buffers/ide-buffer-manager.c
index fa5142dd1..56aa21421 100644
--- a/src/libide/buffers/ide-buffer-manager.c
+++ b/src/libide/buffers/ide-buffer-manager.c
@@ -1218,6 +1218,8 @@ ide_buffer_manager_save_file_async (IdeBufferManager     *self,
   IdeContext *context;
   SaveState *state;
 
+  IDE_ENTRY;
+
   if (progress)
     *progress = NULL;
 
@@ -1228,6 +1230,22 @@ ide_buffer_manager_save_file_async (IdeBufferManager     *self,
   g_return_if_fail (!cancellable || G_IS_CANCELLABLE (cancellable));
 
   task = g_task_new (self, cancellable, callback, user_data);
+  g_task_set_source_tag (task, ide_buffer_manager_save_file_async);
+
+  /* Short cirtcuit if there is nothing to do. */
+  if (!gtk_text_buffer_get_modified (GTK_TEXT_BUFFER (buffer)) &&
+      !ide_buffer_get_changed_on_volume (buffer) &&
+      ide_file_equal (file, ide_buffer_get_file (buffer)))
+    {
+      if (progress != NULL)
+        {
+          *progress = ide_progress_new ();
+          ide_progress_set_fraction (*progress, 1.0);
+        }
+
+      g_task_return_boolean (task, TRUE);
+      IDE_GOTO (unmodified);
+    }
 
   context = ide_object_get_context (IDE_OBJECT (self));
   ide_context_hold_for_object (context, task);
@@ -1254,7 +1272,10 @@ ide_buffer_manager_save_file_async (IdeBufferManager     *self,
                                 ide_buffer_manager_save_file__load_settings_cb,
                                 g_object_ref (task));
 
+unmodified:
   unregister_auto_save (self, state->buffer);
+
+  IDE_EXIT;
 }
 
 /**