--ignore-invalid flag to git log et al.?

Junio,

What would you think about a --ignore-invalid flag for things like git rev-list and git log, to tell it to ignore any refs on the command line that are not valid objects?

Currently there is a buglet in gitk where if a user puts some sort of ref on the command line, and then makes the ref invalid (e.g. by deleting the ref if it is a head or tag, or doing a git prune if it is a sha1 ID with no head/tag pointing to it), and then does "Update" in gitk, it will get an error because of the now-invalid ref. (Yes, this is a bit of a corner case, but I have had a user point out this behaviour to me.) With a --ignore-invalid flag, gitk could use this when doing "Update" to avoid the error.

An alternative would be to have some way to validate refs. I don't know how to do that efficiently. I think I would not want to have to do a fork/exec for every ref that I wanted to check.

Thoughts?

Paul.