yes Hunter, exactly this was one possibility. The names of the property can be just like in the HTTP Headers: Last-Modified If-Modified-Since -> maybe here can be also the commit hash, not only time in millis/UTC ETag
and every module may have different value ;-) then. and then the SCM... has to resolve " If-Modified-Since " to the TIME. The missing "..." is some layer useful in the incremental build too.
