What to checksum when submitting an update?

[Tom Limoncelli]

I'm a new maintainer, so please excuse this basic question.

The port I maintain is vcs_blackbox.  It has recently been added to
the system.  I'd like to do my first update.  The change is simply a
version update:

-github.setup        StackExchange blackbox 1.20150203 v
+github.setup        StackExchange blackbox 1.20150222 v

However it isn't clear to me how to update the checksums.  I know the
commands (openssl dgst -sha256 / openssl dgst -rmd160) but what file
gets checksummed?  This package is on github.

By looking at the error messages, it seems that the checksums is of the file at
 http://packages.macports.org/vcs_blackbox/vcs_blackbox-$VERSION.darwin_*.noarch.tbz2
but until the file is there, how do I know I can generate the exact same file?

Are the checksums updated for me or am I going about this the wrong way?

Thanks!
Tom

-- 
Email: tal at whatexit.org    Work: tlimoncelli at StackOverflow.com
Skype: YesThatTom
Blog:  http://EverythingSysadmin.com