Store properties in a more appropriate directory on Mac and Linux

[lukeu]

Reported to me: "On my Mac, TracInstant tries to store the config file in the directory". That is an odd location because it is in the top-level directory of my account:

/Users/foo/bettyluke.net/TracInstant/TracInstant.properties

Indeed, it falls back to that when it can't find the Windows-specific Application Data\Roaming folder.

It looks like on Mac to use:

$(HOME)/Library/Application Support/

And on Linux I guess "the right thing" would be to make it a hidden folder. Possibly:

    ~/.TracInstant/TracInstant.properties

[japanoise]

And on Linux I guess "the right thing" would be to make it a hidden folder. Possibly:

    ~/.TracInstant/TracInstant.properties

On linux the right thing to do would be to respect $XDG_CONFIG_DIR, or put a directory in .config otherwise: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

There is likely a library to "do the right thing" in respecting $XDG_CONFIG_DIR, but I'm not 100% up on my Java so that's an exercise for the reader ;)

[japanoise]

Very silly pseudocode:

    protected File getGeneralDataDirectory() throws IOException {
        File baseDir = null;
        String homePath = (String) System.getProperties().get("user.home");
#ifdef windows
        if (homePath != null) {
            baseDir = new File(homePath);
        }
        if (baseDir == null || !baseDir.isDirectory()) {
            throw new IOException("User home directory not found.");
        }
        File f = new File(baseDir, "Application Data");
        return f.isDirectory() ? f : baseDir;
#ifdef linux
        String configPath = System.getEnvironmentVariable("XDG_CONFIG_DIR")
        if (configPath.equals("")) configPath = homePath+"/.config/TracInstant/"
        else configpath += "/TracInstant"
        File f = new File(configPath, "Application Data");
        return f.isDirectory() ? f : baseDir;
}