brew.sh: handle Linux systems with no 'locale'

[maxim-belkin]

such as Alpine Linux

Closes Linuxbrew/docker#83

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[sjackman]

Use command -v rather than which.

[maxim-belkin]

Let me know which commit to keep:

• 9abe3ee: suppresses error stream but should have the same effect,
• 376227b: checks for locale explicitly.

[MikeMcQuaid]

👏🏻 Easy! Thanks again!

[sjackman]

I'm not a fan of suppressing all error messages from locale in this way.

[maxim-belkin]

Do you suggest removing 2>/dev/null here?

[MikeMcQuaid]

Can you explain why @sjackman? When we're just using the output to decide on a variable and we have an else: what's the upside of showing errors here?

[sjackman]

For troubleshooting. We do not expect locale to fail, and if it were to fail for some unexpected reason, and the user were to report an issue, we would have no basis on which to troubleshoot that failure, because stderr was unconditionally suppressed, which is the shell equivalent of catching all exceptions and ignoring them.

[MikeMcQuaid]

We're not checking the exit code of locale as-is just checking (twice) if the output contains a string. It doesn't matter to us whether the output doesn't contain that string due to a failure or due to the locale being missing. Considering how we've been printing these warnings at users in the past and causing unnecessary confusion: I'd rather we didn't continue to do so.

[sjackman]

We have a difference of opinion here, and that's okay. I prefer not to suppress stderr, but I'm fine merging either.

[sjackman]

Thank you, Maxim!

[MikeMcQuaid]

This isn't correct behaviour on macOS, unfortunately.

[sjackman]

Under what circumstances does command -v locale fail on macOS? I believe that situation is impossible with SIP enabled.

[MikeMcQuaid]

It is hence I'd like to avoid the check.

[maxim-belkin]

I can rewrite this part using if [[ -n "$HOMEBREW_MACOS" ]]; then ... else ... {complex logic}; fi -- would that work?

[MikeMcQuaid]

Yeh, go for it. I'm still of the belief that checking for locale is pointless where we're correctly handling the case when it doesn't exist anyway if we hide the errors.

[MikeMcQuaid]

I'll defer to @sjackman on Linux behaviour but macOS needs to be the same as before.

[sjackman]

Looks great! Thank you, Maxim.

[maxim-belkin]

Thank you both!