--diagnostic-width= depends on the terminal settings, and it shouldn't affect compilation. However, sccache includes this flag in hash computation. It means these two commands don't share cache:

# 1. include `--diagnostic-width=` for TTY terminals
cargo build

# 2. exclude `--diagnostic-width=`. No cache hits!
cargo build > _.log 2>&1

Could we have an sccache option to remove the --diagnostic-width= parameter from hash computation?