Add APIC frame support to 'get' command

[ikalnytskyi]

APIC frame contains a picture of one of the media file covers. Currently APIC frame support is limited by 'set' command, but not 'get'. We have to figure out the best way to support APIC frame in 'get' command.

At this point two options are considered:

• Returning a picture from APIC frame inline in base64 form
• Returning a picture from APIC frame as a temporary file with a reference to it in the metadata text

[ikalnytskyi]

@malor I wonder what your opinion on this?

[malor]

I want to say a temporary file (some graphical terminal emulators would even recognize a link and make it clickable?), but it's not clear to me who and when is supposed to clean it up later. It's a temporary directory, yes, but multiple calls to get would keep such pics around until the next machine reboot?

[ikalnytskyi]

I want to say a temporary file (some graphical terminal emulators would even recognize a link and make it clickable?)

Text wrapped into OSC 8 is considered to be a hyperlink by supported terminals. I think this a good idea to provide such functionality.

It's a temporary directory, yes, but multiple calls to get would keep such pics around until the next machine reboot?

Yeah, correct. We can probably implement proper cleanup for 'edit' command by calling 'unlink()' on the file just right after we opened it, but it cannot be applied to 'get' command.

I think we can probably live with that until we implement a better solution. Or maybe considering an extra flag to support base64 format too.