Add prog option to argparse for help messages

[jack-champagne]

When running cantools, depending on how it is launched, the help message will give different program names after the word usage: which can be set to a distinct name. Instead of deferring this to the default (os.path.basename(sys.argv[0])) in argparse, specify program name explicitly in argparse options.

Before:

$ python -m cantools --help
usage: __main__.py [-h] [-d] [--version] {decode,monitor,plot,convert,dump,generate_c_source,list} ...

Various CAN utilities.
...

(pip installed)

$ cantools --help
usage: cantools [-h] [-d] [--version]
                {decode,monitor,dump,convert,generate_c_source} ...

Various CAN utilities.
...

After:

$ python -m cantools --help
usage: cantools [-h] [-d] [--version] {decode,monitor,plot,convert,dump,generate_c_source,list} ...

Various CAN utilities.
...

(pip installed)

$ cantools --help
usage: cantools [-h] [-d] [--version] {decode,monitor,plot,convert,dump,generate_c_source,list} ...

Various CAN utilities.
...

[andlaus]

hm, I'm only 90% sure that this is an improvement: if cantools is called in non-standard ways, the usage message would be off if is done like this. currently it is correct:

ln -s ~/.local/bin/cantools ct
./ct --help
usage: ct [-h] [-d] [--version] {generate_c_source,convert,list,dump,plot,decode,monitor} ...
[...]

I think this is pretty much a corner case, though. any opinions @zariiii9003, @juleq?

[jack-champagne]

This is a good point, maybe instead of my change, just a check to avoid it showing __main__.py when launched this way. I see the benefit of it showing the exec name. What do you think?

[andlaus]

I guess it would be a good solution. That said, I think that the current patch is acceptable if @zariiii9003 and @juleq do not object...

[zariiii9003]

I guess it would be a good solution. That said, I think that the current patch is acceptable if @zariiii9003 and @juleq do not object...

I do not object, looks okay to me.

[andlaus]

alright, let's go for it. Merging, thanks @jack-champagne