Also known as "forward history searching", this enhancement brings to the libsvn_fs API the ability to traverse the chain of "interesting history points" for a line of versioned history in an oldest-to-youngest fashion. Today's API allows only the opposite: starting with a path/revision pair, walk backwards through the past changes in that line of history. This functionality flows naturally out of the current FS design, which stores for each node-revision a reference to that node-revision's predecessor node-revision. Currently there is no FS-level storage of the reverse-link -- the successor node-revisions. And yes, there's a 1-to-many relationship of node-revisions to their successors because successors are created both by modifications to a versioned item and by copying those items elsewhere (which can happen any number of times).