spurious downloading lines in mach output from builders

[metajack]

See http://build.servo.org/builders/gonk/builds/29/steps/compile/logs/stdio for an example. Can we detect that we're not on a real terminal and then not do overwrites in that case?

[SimonSapin]

Do you mean the Downloading Rust snapshot: lines? We already have such a switch. They can be disabled with a TERM=dumb environment variable.

This switch could probably be smarter, maybe using sys.stdout.isatty()

[SimonSapin]

This was probably fixed in #5043, but I didn’t manage to find a newer builder log that downloads Rust. Do the builders cache Rust snapshots?

[jdm]

@larsbergstrom Do you know the answer?

[larsbergstrom]

Sadly, I believe we do not cache the Rust snapshots - they are in the build/.servo directory, and the build/ directory is blown away every time. We may want to do something similar to @Manishearth's changes to keep the .cargo directory global (servo/saltfs#19 ) to avoid this problem.

[jdm]

Downloading Rust snapshot...
Extracting Rust snapshot...
Snapshot Rust ready.

from http://build.servo.org/builders/linux1/builds/989/steps/compile/logs/stdio

[mbrubeck]

Filed #5200 for caching Rust snapshots outside of the working dir.