RFR: 8350007: Add usage message to the javadoc executable [v2]

[Hannes Wallnöfer]

On Fri, 14 Feb 2025 11:50:27 GMT, Nizar Benalla <nbenalla at openjdk.org> wrote:

>> This patch adds a new message when you run the `javadoc` executable with any arguments.
>> Currently, unlike most other tools, running `javadoc` without any arguments does not show you how to use the tool or point you to use the `--help` option, this can be improved.
>> 
>> Before change:
>> 
>> W $ ./javadoc
>> error: No modules, packages or classes specified.
>> 1 error
>> 
>> 
>> After change:
>> 
>> W $ ./javadoc
>> Usage:
>>     javadoc [options] [packagenames] [sourcefiles] [@files]
>> For additional help on usage:           javadoc --help
>
> Nizar Benalla has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update test with new usage message

src/jdk.javadoc/share/classes/jdk/javadoc/internal/tool/resources/javadoc.properties line 39:

> 37: main.no-arg=Usage:\n\
> 38: \    javadoc [options] [packagenames] [sourcefiles] [@files]\n\
> 39: For additional help on usage:           javadoc --help

Maybe call the property `main.usage.short` to tie it to the main usage message above and make it clear they should be kept in sync? 

The extra whitespace in the second line looks unmotivated. Could we use the existing `main.for-more-details-see-usage` message below instead of the second line?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/23618#discussion_r1959974402