lib/config: Rename change-update-summary to auto-...

Mildly bikeshed, though I find the name `auto-update-summary` to be
easier to grok than `change-update-summary`. I think it's because it can
be read as "verb-verb-noun" rather than "noun-verb-noun".

Closes: #1693
Approved by: mwleeds

src/libostree/ostree-repo-commit.c

@@ -2202,7 +2202,7 @@ ostree_repo_commit_transaction (OstreeRepo                  *self,
       return FALSE;
   g_clear_pointer (&self->txn.collection_refs, g_hash_table_destroy);
 
-  /* Update the summary if change-update-summary is set, because doing so was
+  /* Update the summary if auto-update-summary is set, because doing so was
    * delayed for each ref change during the transaction.
    */
   if (!_ostree_repo_maybe_regenerate_summary (self, cancellable, error))

src/libostree/ostree-repo.c

@@ -5387,7 +5387,7 @@ summary_add_ref_entry (OstreeRepo       *self,
  *
  * It is regenerated automatically after a commit if
  * `core/commit-update-summary` is set, and automatically after any ref is
- * added, removed, or updated if `core/change-update-summary` is set.
+ * added, removed, or updated if `core/auto-update-summary` is set.
  *
  * If the `core/collection-id` key is set in the configuration, it will be
  * included as %OSTREE_SUMMARY_COLLECTION_ID in the summary file. Refs that
@@ -5593,23 +5593,21 @@ ostree_repo_regenerate_summary (OstreeRepo     *self,
   return TRUE;
 }
 
-/* Regenerate the summary if `core/change-update-summary` is set */
+/* Regenerate the summary if `core/auto-update-summary` is set */
 gboolean
 _ostree_repo_maybe_regenerate_summary (OstreeRepo    *self,
                                        GCancellable  *cancellable,
                                        GError       **error)
 {
-  gboolean update_summary;
+  gboolean auto_update_summary;
 
   if (!ot_keyfile_get_boolean_with_default (self->config, "core",
-                                            "change-update-summary", FALSE,
-                                            &update_summary, error))
+                                            "auto-update-summary", FALSE,
+                                            &auto_update_summary, error))
     return FALSE;
 
-  if (update_summary && !ostree_repo_regenerate_summary (self,
-                                                         NULL,
-                                                         cancellable,
-                                                         error))
+  if (auto_update_summary &&
+      !ostree_repo_regenerate_summary (self, NULL, cancellable, error))
     return FALSE;
 
   return TRUE;