public static CommitSelectionExpression BeforeTag(
this CommitSelectionExpression parentExp, string tag)
{
var commitWithTag = parentExp.Fixed().WithTags(tag).SingleOrDefault();
if (commitWithTag == null)
{
return(parentExp.Reselect(c => c.Take(0)));
}
return(parentExp.BeforeRevision(commitWithTag.Revision));
}