diff: Port some to new code style

Continuing to chip away at this.  Using `g_file_enumerator_iterate()`
here helps notably.

I started on the much bigger `ostree_diff_dirs_with_options()` but
it's a lot messier - for later.

Closes: #844
Approved by: jlebon

src/libostree/ostree-diff.c

@@ -35,9 +35,7 @@ get_file_checksum (OstreeDiffFlags  flags,
                    GCancellable *cancellable,
                    GError   **error)
 {
-  gboolean ret = FALSE;
   g_autofree char *ret_checksum = NULL;
-  g_autofree guchar *csum = NULL;
 
   if (OSTREE_IS_REPO_FILE (f))
     {
@@ -52,27 +50,26 @@ get_file_checksum (OstreeDiffFlags  flags,
         {
           if (!glnx_dfd_name_get_all_xattrs (AT_FDCWD, gs_file_get_path_cached (f),
                                              &xattrs, cancellable, error))
-            goto out;
+            return FALSE;
         }
 
       if (g_file_info_get_file_type (f_info) == G_FILE_TYPE_REGULAR)
         {
           in = (GInputStream*)g_file_read (f, cancellable, error);
           if (!in)
-            goto out;
+            return FALSE;
         }
 
+      g_autofree guchar *csum = NULL;
       if (!ostree_checksum_file_from_input (f_info, xattrs, in,
                                             OSTREE_OBJECT_TYPE_FILE,
                                             &csum, cancellable, error))
-        goto out;
+        return FALSE;
       ret_checksum = ostree_checksum_from_bytes (csum);
     }
 
-  ret = TRUE;
   ot_transfer_out_value(out_checksum, &ret_checksum);
- out:
+  return TRUE;
-  return ret;
 }
 
 OstreeDiffItem *
@@ -130,28 +127,22 @@ diff_files (OstreeDiffFlags  flags,
             GCancellable    *cancellable,
             GError         **error)
 {
-  gboolean ret = FALSE;
   g_autofree char *checksum_a = NULL;
   g_autofree char *checksum_b = NULL;
-  OstreeDiffItem *ret_item = NULL;
-
   if (!get_file_checksum (flags, a, a_info, &checksum_a, cancellable, error))
-    goto out;
+    return FALSE;
   if (!get_file_checksum (flags, b, b_info, &checksum_b, cancellable, error))
-    goto out;
+    return FALSE;
 
+  g_autoptr(OstreeDiffItem) ret_item = NULL;
   if (strcmp (checksum_a, checksum_b) != 0)
     {
       ret_item = diff_item_new (a, a_info, b, b_info,
                                 checksum_a, checksum_b);
     }
 
-  ret = TRUE;
   ot_transfer_out_value(out_item, &ret_item);
- out:
+  return TRUE;
-  if (ret_item)
-    ostree_diff_item_unref (ret_item);
-  return ret;
 }
 
 static gboolean
@@ -160,47 +151,38 @@ diff_add_dir_recurse (GFile          *d,
                       GCancellable   *cancellable,
                       GError        **error)
 {
-  gboolean ret = FALSE;
+  g_autoptr(GFileEnumerator) dir_enum =
-  GError *temp_error = NULL;
+    g_file_enumerate_children (d, OSTREE_GIO_FAST_QUERYINFO,
-  g_autoptr(GFileEnumerator) dir_enum = NULL;
+                               G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-  g_autoptr(GFile) child = NULL;
+                               cancellable,
-  g_autoptr(GFileInfo) child_info = NULL;
+                               error);
-
-  dir_enum = g_file_enumerate_children (d, OSTREE_GIO_FAST_QUERYINFO, 
-                                        G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-                                        cancellable, 
-                                        error);
   if (!dir_enum)
-    goto out;
+    return FALSE;
 
-  while ((child_info = g_file_enumerator_next_file (dir_enum, cancellable, &temp_error)) != NULL)
+  while (TRUE)
     {
+      GFileInfo *child_info;
       const char *name;
 
+      if (!g_file_enumerator_iterate (dir_enum, &child_info, NULL,
+                                      cancellable, error))
+        return FALSE;
+      if (child_info == NULL)
+        break;
+
       name = g_file_info_get_name (child_info);
 
-      g_clear_object (&child);
+      g_autoptr(GFile) child = g_file_get_child (d, name);
-      child = g_file_get_child (d, name);
-
       g_ptr_array_add (added, g_object_ref (child));
 
       if (g_file_info_get_file_type (child_info) == G_FILE_TYPE_DIRECTORY)
         {
           if (!diff_add_dir_recurse (child, added, cancellable, error))
-            goto out;
+            return FALSE;
         }
-      
-      g_clear_object (&child_info);
-    }
-  if (temp_error != NULL)
-    {
-      g_propagate_error (error, temp_error);
-      goto out;
     }
 
-  ret = TRUE;
+  return TRUE;
- out:
-  return ret;
 }
 
 /**