identify: build the tag list directly instead of using wctx.tags()
The current implementation of workingctx.tags() returns the tags of the parents.
This causes the calculation of {lastesttagdistance} from wdir() to be wrong.
The value when updated to a tag is 0, but updated to the tag's child is 2, the
child of that 3, and so on. This prepares for workingctx.tags() to not report
the parent tags.
% creating repo
% add and commit
C test.py
% change
M test.py