--check-input-hash exit code confusion

[ctcjab]

According to the --help output for conda-lock --check-input-hash,

If no files were updated exit with exit code 4

However, conda-lock appears to be exiting 0 in this case.

Zero is better than nonzero because it allows using conda-lock as a pre-commit hook. If conda-lock were to exit nonzero in this case, the pre-commit hook would always fail.