dirstate-item: factor some code in the C implementation...
dirstate-item: factor some code in the C implementation
We have both `dirstate_item_from_v1_meth`, a class method, and
`dirstate_item_from_v1_data`, a function taking low level C argument.
Lets implement the former with the later.
Differential Revision:
https://phab.mercurial-scm.org/D11385