Add optional json output format

[anderejd]

--json or something similar.

[icefoxen]

Related: #10

This would be nice for my side-project too; aim me at the right data structures and if/when I need this I'll implement it. Do we want this to be a feature flag so we don't always need to build serde, or is that fine?

[anderejd]

aim me at the right data structures and if/when I need this I'll implement it.

All the functions related to printing the tree needs to be separated from the source code scanning, in particular this function needs some refocusing:
https://github.com/anderejd/cargo-geiger/blob/master/src/lib.rs#L829

When that separation is done the json feature should only require a bit of serde attribute sprinkling on top.

Do we want this to be a feature flag so we don't always need to build serde, or is that fine?

I think it's good to have it on by default, cargo-geiger already depends on serde and serde-json... and most of the remaining crates on crates.io.

[stephaneyfx]

Should this be closed given that #115 was merged?

[anderejd]

Yes! :)