There are two cases:
1. It seems that grep on macOS exits as soon as it finds the first match. This makes cargo unhappy and it prints message like "failed printing to stdout: Broken pipe (os error 32)". The solution is to fully consume the output from cargo. I choose to use tee for this task.
2. When in a strict mode, bash complains that $1 is not defined (when it's actually not defined in case of omitting --install). The solution is to apply bash substitution magic: when $1 is undefined or set to null substitute it with empty string.
- Add a check-rustfmt.sh script which checks if the right version of
rustfmt is installed.
- Run check-rustfmt.sh --install as an install step under travis_wait.
This is to work around the issue where cargo takes forever to build
rustfmt, causing Travis to terminate the build because it hasn't
produced any output for 10 minutes.
