Feature request: print features used to build each crate in tree

[Dushistov]

Thanks for this tool,

to debug issue like desribed at rust-lang/cargo#4323 it would be nice
to show in cargo tree output the features used for building each crate
(it can be done by parsing cargo check -v output),

for example if cargo tree has such feature, then SO question can be solved just compare cargo tree outputs,
in one case it may print something like:

nom v3.1.0 ["std", "memchr", "stream"]

in other case

nom v3.1.0 ["std", "memchr", "stream", "verbose-errors"]

[sfackler]

That seems like a reasonable thing to do!

[psinghal20]

Hi! I wanted to know if someone is working over this feature request? If not, maybe I can contribute to this issue. Any tips to proceed would be helpful!

[brson]

In addition to knowing which features are on, I think it would be useful to know which features are off too. Let me see the entire "feature-space".

e.g. for @psinghal20's work on tikv/tikv#4167, they are trying to adjust features to remove bloat, and there are often 'negative' features that could disable code, that one might not know about.