Merge lp:~mterry/duplicity/giobackend-display-name into lp:~duplicity-team/duplicity/0.8-series

[Michael Terry]

I was doing some testing on the google-drive: GIO backend (this is not the gdoc: duplicity backend, but rather using GNOME's abstraction layer to talk to Google through the giobackend code) and noticed some problems.

(A) Getting a list of files was broken because the google-drive: GIO backend chooses to use internal IDs for all its filename. Only the display_name() call gets the real user-set filename. Which, OK. We can use that instead. This will work for google-drive: as well as all other backends, since that is the user-set/user-visible name that we want to work with anyway.

(B) Getting files wasn't working because we had been passing NOFOLLOW_SYMLINKS. Apparently the google-drive: GIO backend treats all internal files as symlinks to other internal files? Doesn't matter, we can avoid having to care about what a backup does in that regard by simply not passing that flag. It was a level of precaution that we don't really need. Normally, duplicity will always be dealing with real files. If it's trying to get a symlink, it's because the user manually created one. In which case, maybe we should follow it, since the user wants us to.

Together, these fixes let google-drive: work (and maybe other similarly bizarre GIO backends). I also tested on a couple other backends (SSH and local) and they worked fine still.

=== modified file 'duplicity/backends/giobackend.py'
--- duplicity/backends/giobackend.py	2017-02-20 00:05:17 +0000
+++ duplicity/backends/giobackend.py	2017-08-05 21:47:05 +0000
@@ -116,8 +116,11 @@
 
     def __copy_file(self, source, target):
         from gi.repository import Gio  # @UnresolvedImport
+        # Don't pass NOFOLLOW_SYMLINKS here. Some backends (e.g. google-drive:)
+        # use symlinks internally for all files. In the normal course of
+        # events, we never deal with symlinks anyway, just tarballs.
         source.copy(target,
-                    Gio.FileCopyFlags.OVERWRITE | Gio.FileCopyFlags.NOFOLLOW_SYMLINKS,
+                    Gio.FileCopyFlags.OVERWRITE,
                     None, self.__copy_progress, None)
 
     def _error_code(self, operation, e):
@@ -150,12 +153,18 @@
     def _list(self):
         from gi.repository import Gio  # @UnresolvedImport
         files = []
-        enum = self.remote_file.enumerate_children(Gio.FILE_ATTRIBUTE_STANDARD_NAME,
-                                                   Gio.FileQueryInfoFlags.NOFOLLOW_SYMLINKS,
+        # We grab display name, rather than file name because some backends
+        # (e.g. google-drive:) use filesystem-specific IDs as file names and
+        # only expose the "normal" name as display names. We need the display
+        # name, because we try to parse them. If the backend does this sort of
+        # trickery, it will accept both versions of the filename, so we
+        # shouldn't get into any trouble doing this.
+        enum = self.remote_file.enumerate_children(Gio.FILE_ATTRIBUTE_STANDARD_DISPLAY_NAME,
+                                                   Gio.FileQueryInfoFlags.NONE,
                                                    None)
         info = enum.next_file(None)
         while info:
-            files.append(info.get_name())
+            files.append(info.get_display_name())
             info = enum.next_file(None)
         return files