Allow for tracks to be added recursively from library

[Porkepix]

When using shift + L to add all the tracks from a directory to the playlist, it do work for the first level (ie. all tracks included in that directory), but it doesn't work for directories in that directory that also have tracks, and probably doesn't either for directories in levels below.

shift + L could walk directories recursively to get all the musics included in the whole tree. It just needs to be careful with links to don't go into deadlocks/infinite loops/counting several times the same files.

[tramhao]

It's a good idea and I'll look into it. Thanks for the feedback.

[Porkepix]

Also, note that tools such as fd and ripgrep already solved some of these issues (my initial remark was because I already reported issues on such tools in some corner cases).

[hasezoey]

i didnt notice there was a issue for this already (so i closed mine #164)

this should be easily enough to be added, but there are some questions:

• how should links be handled (especially self-referential (soft-)links)
• should there be a limit to how deep something goes
• should there be a limit to only be for the same device (find -xdev)

and maybe anything i have missed?

self-referential link example:

$ mkdir test
$ cd test
$ mkdir level1
$ cd level1
$ ln -sfr ../
$ cd test/level1/test
$ pwd
/test/level1/test/level1/test