Utils: shortened brew paths

[alebcay]

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Overview

This PR adds:

• New file in Utils module, utils/path
  • Utils.path_is_parent_of? determines if one Pathname/String is a parent of another Pathname/String
  • Utils.shortened_brew_path expresses a Pathname/String as a shell expansion where possible, e.g. /usr/local/Cellar/cmake as $(brew --cellar)/cmake. Where possible, it can also express a Pathname as a formula's opt prefix, e.g. /usr/local/opt/openjdk/libexec/openjdk.jdk/Contents/Home becomes $(brew --prefix openjdk)/libexec/openjdk.jdk/Contents/Home
• Methods in language/java
  • Language::Java.short_java_home_shell, Language::Java.short_java_home_env, Language::Java.overridable_short_java_home_env which are shortened versions of the existing respective methods

This PR also modifies write_env_script, write_exec_script, and write_jar_script to use shortened_brew_path.

Rationale

Now that we are bottling everything, there are many cases where we can't use all: bottles because an env script, exec script, jar script etc. has a platform-dependent HOMEBREW_PREFIX in it (e.g. /usr/local vs /opt/homebrew).

The result is that we have to carry extra copies of some bottles where the bulk of the payload is the same. This is especially the case in Java based formulae, where the resulting bottle can be tens or hundreds of megabytes in size.

Commands like $(brew --prefix), $(brew --cellar), etc. don't invoke the full Homebrew installation (they short-circuit to shell script instead), so using these where possible in scripts makes the resulting bottle portable while adding minimal performance cost.

A resulting env script might look something like this:

#!/bin/bash
JAVA_HOME="${JAVA_HOME:-$(brew --prefix openjdk)/libexec/openjdk.jdk/Contents/Home}" exec "$(brew --cellar)/mill/0.9.8/libexec/mill"  "$@"

I'm especially open to input on the naming of any of the new methods introduced in this PR. Wasn't really sure about a most suitable name so just went with my gut for now.

Note: I'm not happy with the tests for the additional Java methods right now. In the test env, they evaluate to $(brew --prefix)/opt/openjdk/libexec/... when in practice (from testing with formulae) it actually produces a more desired $(brew --prefix openjdk)/libexec/.... Both are technically correct (when openjdk is installed), but just wanted to point out this slight discrepancy. I think this is due to how the openjdk formula is being mocked in that test, but after trying to manually set up folders/symlink them where appropriate in the test, I still couldn't get it working exactly as desired.

[BrewTestBot]

Review period will end on 2021-06-16 at 01:53:16 UTC.

[MikeMcQuaid]

I like the idea but implementation needs some tweaks!

[alebcay]

Moved some things around. Now the new methods live in utils/path.

[MikeMcQuaid]

Great work! 🎉

[BrewTestBot]

Review period ended.