Small documentation issues regarding java options

[mrckzgl]

Wiki issue

In https://github.com/jruby/jruby/wiki/JRuby-Java-Options-Files and https://github.com/jruby/jruby/wiki/ConfiguringJRuby is mentioned to use -J<option> to pass options to the JVM. However, the example in the second url is -J-Xmx2G which would translate to the generic case as -J-<option>. Is that a bug in the docs, or are both valid -J-Xmx2G and -JXmx2G? In the latter case it would also be nice to be fully documented.

EDIT: Ah sorry, realize how that is meant now. <option> includes the -. This is needed, as there are options which include two minuses. So this is not an issue anymore I guess. Except, it would be nice to include the example in the first wiki url too, or even explicitly specify that <option> includes all minuses? The other issues below, however, are independent thereof and still existing.

Command line help issues

Using jruby 9.4.1.0 (3.1.0) 2023-02-07 237d5fa5f4 Java HotSpot(TM) 64-Bit Server VM 15.0.2+7-27 on 15.0.2+7-27 +jit [x86_64-linux] there are a few minor issues with the --help output:

-J[java option]                                     pass an option on to the JVM (e.g. -J-Xmx512m)/nuse --properties to 
                                                       JRuby properties run 'java -help' for a list of other Java options

is /n meant to be a line break \n ? But still, further use --properties to JRuby properties run 'java -help' for a list of other Java options is no proper gramatically correct sentence. Seems these are two sentences. But even then, the first is no correct sentence (use --properties to JRuby properties).

--properties                                        List all configuration Java properties (prepend "jruby." when 
                                                       directly to Java)

(prepend "jruby." when directly to Java) does not make sense / is no proper sentence. But I would probably omit that bracket here, as it only makes sense in combination with the output of --properties.

Looking at --properties reveals another little inconsistency:

# Specify them by passing -X<property>=<value>
#   or if passing directly to Java, -Djruby.<property>=<value>

Is it really -Djruby.<property>=<value>? That would contradict (prepend "jruby." when directly to Java) and also -D is not listed as command line option via --help at all. Is it possible that -Xjruby.<property>=<value> is meant?

Last but not least one substantive question in this regard: What is the difference of specifying a java option via -X<property>=<value> vs. -[D/X]jruby.<property>=<value> ?

[headius]

<option> includes the -

I don't think there's anything else to do here. Both pages refer to -J<option> and the "ConfiguringJRuby" page includes examples. If you have some suggested text for the "JRuby Java Options Files" page, let us know!

is /n meant to be a line break

Looks like this was a change from when we manually formatted the help lines to a new pageable formatter in #7458. I will modify it to use semicolons so as not to interfere with the paging output.

(prepend "jruby." when directly to Java) does not make sense

The -Xfoo.bar format is just a shortcut for -J-Djruby.foo.bar. I will clean up the text a bit to make this clearer.