Miscellaneous fixes for try subcommand.

The first commit is independent of the rest, the last one depends on the second one and could be squashed with it but I preferred to keep them separate just in case.

The commit messages should hopefully be self-explanatory.
Unfortunately I think it _is_ a concern (personally I never use paths with spaces as it's just a recipe for disaster, so not for me, but I'm pretty sure this would bite others) and `shlex` doesn't really help because it treats backslashes as escape characters, meaning that it totally mangles Windows paths.

So either this option would need to be documented to escape backslashes or I'd have to write my own tokenization code. Neither seems really appealing.

Would anybody have any other ideas? TIA!