util: add optional path auditor argument to canonpath
The canonpath function will default to creating its own path auditor,
but in some cases it will be useful to use a specialized auditor,
e.g., one that wont abort if a path lies within a subrepository.
% Repository data:
Some stuff to ponder very carefully.
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Copyright 2046, The Masters
Some stuff to ponder very carefully.
M stuff.txt
% Problem encoding:
abort: missing header "Copyright 2046, The Masters" in morestuff.txt
M stuff.txt
A morestuff.txt