Error when not using full SHA in set-commits

[elramen]

When using set-commits as follows: sentry-cli releases set-commits "2.0" --commit "myRepo@be70b3b..25331bb", it looks like everything is working (no error or warning). However, because the provided commit SHAs aren't the full ones, it doesn't actually work. Hence, it would be great to output an error when the provided commit SHAs aren't the full ones.

Note: the docs mention that the full SHA is needed, but that's easy to miss.

[szokeasaurusrex]

It looks like we are parsing the commit hashes locally, so we could probably do this. Although, we should probably also improve error detection server side, since if the provided commits don't exist on the server, there is no error message