persistent-nodemap: properly ignore non-existent `.nd` data file...
persistent-nodemap: properly ignore non-existent `.nd` data file
This code was meant to handle the case of a nodemap docket file
pointing to a nodemap data file that doesn’t exist (anymore),
but most likely caused an `UnboundLocalError` exception instead
when `data` was used on the next line without being defined.
This case is theoretically possible with a race condition
between two hg processes, but is hard to reproduce or test:
* Process A reads a docket file and finds a UID in it
that points to a given data file name.
* Process B decides that this same data file needs compacting.
It writes a new one with a different UID,
overwrites the docket file,
then removes the old data file.
* Only then process A tries to a open a file that doesn’t exist anymore.
Differential Revision:
https://phab.mercurial-scm.org/D9533
