Implement lock file; improve trap management

[friendly-bits]

• Implement lock file check, creation, removal
• Create the trap only for actions which need it
• stop(): kill any running adblock-lean PID's
• status(): check the lock file and if it exists then report on it and exit
• status(): support additional return codes
• Only load config for actions which need it

[lynxthecat]

Would you mind amending the functions to:

x()
{
…
}

[friendly-bits]

Would you mind amending the functions to

Done

[lynxthecat]

Thanks for this. Looks pretty good from a very cursory read through whilst gardening.

[friendly-bits]

Changed function declarations to

f ()
{
...
}

[friendly-bits]

Updated with slightly more compact variable assignment in report_pid_action().

[friendly-bits]

^ Yet more tinkering with code compaction in report_pid_action() :)
I think that's it.

[friendly-bits]

^ Updated with more granular actions set in the lock file.
(and also slightly less spam in the log - we should consider reducing log spam further by utilizing the new print_msg() function for some of the less important messages, rather than log_msg())

[friendly-bits]

^ Fixed incorrect variable name in log_msg() (was _msg, should be msg).

[lynxthecat]

Should be able to test soon. Maybe @Wizballs might also be able to test too.

[friendly-bits]

^

• mk_lock(): Only create the directory for the lock file if it doesn't exist yet (otherwise it could have errored out).
• mk_lock(): Remove trailing . from the action string when writing the action to the lock file.

[Wizballs]

Morning everyone, looks like there has been heaps going on! Sure thing I'll give everything a test run.

[Wizballs]

@lynxthecat Tested multiple different times and service commands with the file lock. I can't find any failure conditions, so I think this PR is good.

@friendly-bits That's really quite neat how it outputs what action is currently being performed. Also I saw another PR where stop/resume/pause was fixed. Tested these also since I was here, all working well again.

[friendly-bits]

^

• Action stop: require cleanup (it wasn't removing /var/run/adblock-lean/)
• status(): swap return code 1 and return code 3 for consistency and so return code 1 means 'error' as per standard

(sorry, I found the issue with stop and then I also wanted to change the return codes of status. should be good to go now)

[friendly-bits]

^ Change function name from advert_action to reg_action.

[friendly-bits]

^

• Fix restart/reload when adblock-lean is running
• Fix the resume action when blocklist compression is enabled

[lynxthecat]

Seems to work well. This evidently required some careful thought and coding. Terrific job @friendly-bits!