Code review comment for lp:~parthm/bzr/300062-better-handling-for-invalid-ignore-pattern

It seem to me that the majority prefers bzr to be more forgiving about bad patterns. I can go ahead with a warning based approach if there are no objections to this over the next day or two.

Here is what I understand.

1. `add` - This should fail (error) as we don't wan't to add file that the user may want to ignore
2. `ignore` - Show warning and skip any bad patterns found on the command line.
3. `ignored` - Try to show ignored files. If this errors out with bad regex, filter out the faulting regex(es) at runtime and retry. The disk files are not changes. Issue a warning about faulting regexes.
4. `status` - If we see a regex failure, filter out the faulting pattern at runtime and retry the ignored files. The retry based approach should reduce the number of 'unknown' files listed.

This would also impact `ls -i/-u`. I will look into that some more. I suppose we would want a similar retry based behavior for this also.

Any further thoughts/ideas about the user interaction should be? Any more commands that might be impacted?