Running scripts on systems with bash version older than v4 causes errors about cargo-semver-checks HOT 3 OPEN

@vasucp1207 can confirm but based on what I saw in the comments I am almost certain they are on Mac OS, which ships an ancient version of Bash by default (3.something, apparently for GPL-avoidance reasons) as well as BSD flavors of command line tools which differ from GNU versions. The missing Cargo.toml is likely due to a difference in sed behavior between Mac and GNU, https://stackoverflow.com/questions/5694228/sed-in-place-flag-that-works-both-on-mac-bsd-and-linux

Writing reliable cross-platform scripts can be a rather tedious rabbit hole to dive into but there are some easy things we can do without going too deep.

• The #!/usr/bin/env bash at the top of the scripts should ensure that some version of bash is running the scripts so I don't think we need to worry about non-bash shells (zsh/fish/nushell etc) unless users go out of their way, e.g. zsh some_script.sh instead of ./some_script.sh.

• Adding a check for Bash version 4+ is simple, basically checking that $BASH_VERSION exists and that ${BASH_VERSINFO[0]} -ge 4. This should also catch any non-bash shells too since they would not set those variables.

• The real tedium comes from trying to ensure that every external tool is installed and supports the required features. I took a brief look into the scripts directory and see grep, sort, curl, jq, and of course sed. There may be more I missed. Not sure this level of effort is worth it for development-only scripts. Perhaps an easier approach would be to document in the Contributing guide that the scripts expect updated bash + a list of the required external programs.

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Great points! If you have a few minutes, would you care to open some PRs for the bash version check and the contributing guide suggestions? I'd be thrilled to merge them.

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#681 mostly addressed this — thank you @jw013! The only open question remaining is if we can do something about our incompatible use of sed.

If I correctly understand the suggested fix at the link you shared, it seems like we might be able to make a copy of the files we intend to edit with sed and apply our change to the copy? Perhaps we make the copy reside in /tmp somewhere, so that a failure of the script won't pollute the git repo?

This is a bit hard for me to test since I don't have a Mac, so I'd love some help. If neither of you @jw013 and @vasucp1207 is up for trying a PR, I can try to whip something up next weekend if I have a bit of time.

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