Colored output support

[epage]

This would be relatively easy while improving the scannability of the results.

[epage]

Maybe https://docs.rs/yansi/0.5.0/yansi/ ?

[epage]

An alternative approach to color is

• https://crates.io/crates/srcerr
• https://crates.io/crates/annotate-snippets This one looks more mature

[epage]

Update on options:

• I looked into annotate-snippets but it doesn't seem to support all of our use cases.
• termcolor is also used by env_logger, so using it here means we aren't adding any dependencies.
• But yansi has a nice API

I'm assuming we'd have CLI arg for forcing on, forcing off with a default of auto-discover. The question is whether to do --color / --no-color like some tools or to mirror ls:

     --color[=WHEN]         colorize the output; WHEN can be 'never', 'auto',
                               or 'always' (the default); more info below

[epage]

See also https://no-color.org/

[epage]

• For interacting with env_logger: https://docs.rs/env_logger/0.8.3/env_logger/#disabling-colors
• For WIndows support: https://docs.rs/yansi/0.5.0/yansi/#windows
• For atty support: https://docs.rs/termcolor/1.1.2/termcolor/#detecting-presence-of-a-terminal
• For env variables: https://github.com/BurntSushi/termcolor/blob/020816f326ed48904e7ed3b37775780039ac3ce2/src/lib.rs#L222