Merge branch 'jt/unparse-commit-upon-graft-change'

Updating the graft information invalidates the list of parents of
in-core commit objects that used to be in the graft file.

* jt/unparse-commit-upon-graft-change:
  commit,shallow: unparse commits if grafts changed

shallow.c

@@ -97,6 +97,13 @@ int commit_shallow_file(struct repository *r, struct shallow_lock *lk)
 {
 	int res = commit_lock_file(&lk->lock);
 	reset_repository_shallow(r);
+
+	/*
+	 * Update in-memory data structures with the new shallow information,
+	 * including unparsing all commits that now have grafts.
+	 */
+	is_repository_shallow(r);
+
 	return res;
 }