dependency order unclear

[alban]

appc/spec says:

The dependencies are applied in order and each image dependency can overwrite files from the previous dependency.

It is not really clear how it works. In rkt/rkt#1752, we have this example of dependencies:

A->B
A->C
A->D

C->B
C->E

D->B
D->E

If we flatten the tree, depth-first, we get the list: A, B, C, E, D. If we flatten the tree, breadth-first, we get the list: A, B, C, D, E. When a file exists in all layers, should we take E's version or D's version? I think the depth-first list makes more sense and we should take E's version.

Another example, with path whitelist:

A->B
A->C
A->D

B->D
B->C

(notice how the order between C and D differs)

The depth-first list is A, B, C, D. If all layers have /file1 and /file2, but B has a path whitelist={/file2}, then /file1 is hidden from B.aci. Does it mean that we should take D's version of /file1 but C's version of /file2?

[jonboulle]

I think it's a little worse than that in that we don't really discuss recursive dependencies at all
https://github.com/appc/spec/blob/master/spec/ace.md#filesystem-setup

Would you mind putting together a proposal to clarify?