Description
Suggestion: CARGO_LOG.
This came up during the Debugging session at Rust Belt Rust. Basically, as soon as people set up their project to use env_logger and set RUST_LOG=debug, they were super confused by the crazy amount of seemingly-random output suddenly on their screen, which appeared to include parse tokens of some sort? The same problem exists at the info level, though obviously to a lesser extent.
While it makes sense for most things to just use RUST_LOG, and it's true that you can solve this problem by specifying a module filter for env_logger, it seems like a common and confusing enough behavior, and a likely enough case that somebody would do RUST_LOG=debug cargo run and get a whole bunch of confusing output, that it likely makes sense to just use a different variable for Cargo.
In fact, while working on a potential PR for this, it happened again to the guy sitting next to me. "What the heck is all this crazy output?" He wasn't a plant or anything!
The only potential downside here is if people expect RUST_LOG to work and it doesn't, but I suspect the number of workflows this would break is vanishingly small and it's a simple fix, so maybe that's not a big deal?
Anyway, PR coming shortly for feedback.