See:
* https://central.sonatype.org/pages/ossrh-eol/
* https://central.sonatype.org/publish/publish-portal-maven/

For the moment, we leave the environment variable names alone, even
though the prefix "OSSRH" is a misnomer now. Reason: it is possible that
the existing OSSRH user tokens were migrated directly. If they don't
work, I'll change this script again to use new environment variables,
and issue a better error if the new variables are missing.

OK, now I'm renaming the credentials, because my first release failed:

  Error: [ERROR] Unable to upload bundle for deployment: Deployment
  [INFO] java.lang.RuntimeException: Invalid request. Status: 401 Response body:
  [INFO]     at org.sonatype.central.publisher.client.httpclient.UploadPublisherEndpoint.call (UploadPublisherEndpoint.java:33)

I am not actually certain the user token changed (it may just be
that the legacy `OSSRH_USER=scijava-ci` value was the culprit), but
that's OK: going through the few orgs that actually deploy to Maven
Central to update to a new token is not really such a big hassle.

I missed some references earlier.

If some env vars are missing, we can still partially write it.
This is especially important if CENTRAL_* vars are missing, but
MAVEN_* vars are present, which as of this writing will be the case
for the vast majority of SciJava-based community projects deploying
to maven.scijava.org, since the transition from OSSRH to Central Portal
is still very recent and many orgs have not yet been updated to match.

We don't need CENTRAL env vars when deploying to maven.scijava.org.
We don't need MAVEN env vars when deploying to Central.

We aren't maintaining it anymore. If you want to keep using Travis CI,
you can pin to an older commit in this repository, or else just fork
the script from just prior to deletion and add it to your repository.

With the upgrade from Nexus v2 to v3, this trick no longer works.
I briefly investigated how to adjust the code to still do it, but
was not immediately successful at doing so. Claude.ai suggests:

    # Invalidate specific paths using the browse API
    # First, you'd need to identify the asset and use:
    curl --netrc -X DELETE \
      "$NEXUS_BASE_URL/service/rest/v1/assets/{assetId}"

But I do not know if this would actually work, and I do not
know how to obtain the assetId for a given resource. We can
figure it out later if needed. But first, let's proceed
without it for a while, to see what problems it creates.

We can't ask maven.scijava.org anymore, because it no longer
proxies Maven Central since the upgrade to Nexus v3.

So instead, we ask Maven Central directly, which works well.

It saddens me to do this. But many of the functions are now broken,
because maven.scijava.org cannot proxy Maven Central any longer, due
to Sonatype deciding that Nexus v3 should be crippleware from now on.

* actions/checkout: v2 -> v4
* actions/setup-java: v3 -> v4
* ensure setup and build scripts run with bash (hard stare at Windows)

See mobie/mobie-viewer-fiji#1104.