Fix the default revision for existing/deleted files when parsing DiffX.
Review Request #11770 — Created Aug. 3, 2021 and submitted
An issue was also found where deleted files in a DiffX were getting a
default revision of
PRE_CREATION, which caused the deleted file to
show up as new. This should have only occurred for newly-created files.
Now, missing revisions show up as
UNKNOWN, making it more clear that
the revision is missing, and avoiding accidentally triggering this bad
Unit tests pass on Python 2 and 3.
Tested this in production and verified that it fixed an issue with a
file appearing as new when it should have appeared as deleted.