maxlabel endpoint does not work for all nodes

[stuarteberg]

If no cleaves or splits were performed on a labelmap instance in a given node, the /maxlabel endpoint does not work for that node.

For instance, the /maxlabel endpoint works fine on node 662e:

http://emdata3:8900/api/node/662e/segmentation/maxlabel

{"maxlabel": 5813044368}

...but not on its child node, 2053:

http://emdata3:8900/api/node/2053/segmentation/maxlabel

No maximum label found for segmentation version 22
 (/api/node/2053/segmentation/maxlabel).

This is not extremely urgent. For now, I have two workarounds at my disposal:

• I can traverse the graph myself, to search for the closest ancestor that has a valid maxlabel, or
• (depending on my usecase) I can get an approximate result by reading the MaxRepoLabel from the /info endpoint.

[DocSavage]

As we discussed earlier, the MaxLabel designation were designed to help eventual remote branches from being re-integrated and are purposely version-specific and capturing the deltas for just that version. I could add an endpoint that does the graph traversal, which is probably a more suitable definition for (cumulative) "max label" at a version.