Jeff King [off-list ref] writes:
...
The rationale for doing this with --no-index is that it is
meant to be used outside a repository, and so parsing revs
at all does not make sense.
This patch gives --untracked the same treatment. While it
_is_ meant to be used in a repository, it is explicitly
about grepping the non-repository contents. Telling the user
"we found a rev, but you are not allowed to use revs" is
not really helpful compared to "we treated your argument as
a path, and could not find it".
Yup, both sounds very sensible. Thanks.