Re: [RFC] Fix alternatives for openjdk{11,17}

[classabbyamp <classabbyamp@users.noreply.github.com>]

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New comment by classabbyamp on void-packages repository

https://github.com/void-linux/void-packages/pull/47416#issuecomment-1829943383

Comment:
basically what needs to happen is:
- if only 1 JRE is installed, it should be `java` and the same for the other JRE programs
- if only 1 JDK is installed, same thing for the JDK tools
- if multiple JREs or JDKs are installed, then the `java` and JDK tools must be the same version.

but because each version is split in 2 packages, it's hard to do.

I think it may be possible to do this with a script (multicall, so it can act as any of the tools) that gets installed in /usr/bin.

Perhaps the alternative group could manage a symlink like `/usr/lib/jvm/openjdk-jre -> /usr/lib/jvm/openjdk##` and `/usr/lib/jvm/openjdk-jdk -> /usr/lib/jvm/openjdk##`, and the script wrapper ensures they're the same version.

```sh
#!/bin/sh

prog="$(basename "$0")"

if [ -e "/usr/lib/jvm/openjdk-jdk" ]; then
    if [ "$(realpath /usr/lib/jvm/openjdk-jdk)" != "$(realpath /usr/lib/jvm/openjdk-jre)" ]; then
        echo "WARNING! JDK/JRE mismatch! use xbps-alternatives to choose one"
    fi
    exec "/usr/lib/jvm/openjdk-jdk/bin/$prog" "$@"
fi

exec "/usr/lib/jvm/openjdk-jre/bin/$prog" "$@"
```
(just spitballing here)