pool_lookup_str
loc = pool_lookup_str(pool, entry, DELTA_LOCATION_DIR);
loc = pool_tmpjoin(pool, loc, loc ? "/" : 0, pool_lookup_str(pool, entry, DELTA_LOCATION_NAME));
loc = pool_tmpappend(pool, loc, "-", pool_lookup_str(pool, entry, DELTA_LOCATION_EVR));
loc = pool_tmpappend(pool, loc, ".", pool_lookup_str(pool, entry, DELTA_LOCATION_SUFFIX));
const char *pool_lookup_str(Pool *pool, Id entry, Id keyname);