Error when not using full SHA in set-commits

[elramen]

When using set-commits as follows: sentry-cli releases set-commits "2.0" --commit "[email protected]", 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.