env_config: use environment variables consistently

- use e.g. `$HOMEBREW_*` for cases where only the environment variable
  is the entire backtick-quoted string
- use e.g. `${HOMEBREW_*}` for cases where the environment variable is
  part of a backtick-quoted string to make clear what parts are variable
  and what parts are not
- use `export HOMEBREW_*=...` for cases where we're talking about
  setting the environment variable (because it likely needs to be
  exported to work how they want)

Inspired by Homebrew/homebrew-bundle#1579 making
similar changes for Homebrew/homebrew-bundle.

Library/Homebrew/cask/config.rb

@@ -16,19 +16,19 @@ class Config
       {
         appdir:               "/Applications",
         keyboard_layoutdir:   "/Library/Keyboard Layouts",
-        colorpickerdir:       "~/Library/ColorPickers",
-        prefpanedir:          "~/Library/PreferencePanes",
-        qlplugindir:          "~/Library/QuickLook",
-        mdimporterdir:        "~/Library/Spotlight",
-        dictionarydir:        "~/Library/Dictionaries",
-        fontdir:              "~/Library/Fonts",
-        servicedir:           "~/Library/Services",
-        input_methoddir:      "~/Library/Input Methods",
-        internet_plugindir:   "~/Library/Internet Plug-Ins",
-        audio_unit_plugindir: "~/Library/Audio/Plug-Ins/Components",
-        vst_plugindir:        "~/Library/Audio/Plug-Ins/VST",
-        vst3_plugindir:       "~/Library/Audio/Plug-Ins/VST3",
-        screen_saverdir:      "~/Library/Screen Savers",
+        colorpickerdir:       "${HOME}/Library/ColorPickers",
+        prefpanedir:          "${HOME}/Library/PreferencePanes",
+        qlplugindir:          "${HOME}/Library/QuickLook",
+        mdimporterdir:        "${HOME}/Library/Spotlight",
+        dictionarydir:        "${HOME}/Library/Dictionaries",
+        fontdir:              "${HOME}/Library/Fonts",
+        servicedir:           "${HOME}/Library/Services",
+        input_methoddir:      "${HOME}/Library/Input Methods",
+        internet_plugindir:   "${HOME}/Library/Internet Plug-Ins",
+        audio_unit_plugindir: "${HOME}/Library/Audio/Plug-Ins/Components",
+        vst_plugindir:        "${HOME}/Library/Audio/Plug-Ins/VST",
+        vst3_plugindir:       "${HOME}/Library/Audio/Plug-Ins/VST3",
+        screen_saverdir:      "${HOME}/Library/Screen Savers",
       }.freeze,
       T::Hash[Symbol, String],
     )

Library/Homebrew/cmd/--cache.rb

@@ -15,7 +15,7 @@ def self.command_name = "--cache"
 
       cmd_args do
         description <<~EOS
-          Display Homebrew's download cache. See also `HOMEBREW_CACHE`.
+          Display Homebrew's download cache. See also `$HOMEBREW_CACHE`.
 
           If a <formula> or <cask> is provided, display the file or directory used to cache it.
         EOS

Library/Homebrew/cmd/cleanup.rb

@@ -13,7 +13,7 @@ class CleanupCmd < AbstractCommand
           Remove stale lock files and outdated downloads for all formulae and casks,
           and remove old versions of installed formulae. If arguments are specified,
           only do this for the given formulae and casks. Removes all downloads more than
-          #{days} days old. This can be adjusted with `HOMEBREW_CLEANUP_MAX_AGE_DAYS`.
+          #{days} days old. This can be adjusted with `$HOMEBREW_CLEANUP_MAX_AGE_DAYS`.
         EOS
         flag   "--prune=",
                description: "Remove all cache files older than specified <days>. " \

Library/Homebrew/cmd/desc.rb

@@ -25,7 +25,7 @@ class Desc < AbstractCommand
                             "it is interpreted as a regular expression."
         switch "--eval-all",
                description: "Evaluate all available formulae and casks, whether installed or not, to search their " \
-                            "descriptions. Implied if `HOMEBREW_EVAL_ALL` is set."
+                            "descriptions. Implied if `$HOMEBREW_EVAL_ALL` is set."
         switch "--formula", "--formulae",
                description: "Treat all named arguments as formulae."
         switch "--cask", "--casks",
@@ -48,7 +48,7 @@ def run
 
         if search_type.present?
           if !args.eval_all? && !Homebrew::EnvConfig.eval_all? && Homebrew::EnvConfig.no_install_from_api?
-            raise UsageError, "`brew desc --search` needs `--eval-all` passed or `HOMEBREW_EVAL_ALL` set!"
+            raise UsageError, "`brew desc --search` needs `--eval-all` passed or `$HOMEBREW_EVAL_ALL` set!"
           end
 
           query = args.named.join(" ")

Library/Homebrew/cmd/info.rb

@@ -27,8 +27,8 @@ class Info < AbstractCommand
         EOS
         switch "--analytics",
                description: "List global Homebrew analytics data or, if specified, installation and " \
-                            "build error data for <formula> (provided neither `HOMEBREW_NO_ANALYTICS` " \
-                            "nor `HOMEBREW_NO_GITHUB_API` are set)."
+                            "build error data for <formula> (provided neither `$HOMEBREW_NO_ANALYTICS` " \
+                            "nor `$HOMEBREW_NO_GITHUB_API` are set)."
         flag   "--days=",
                depends_on:  "--analytics",
                description: "How many days of analytics data to retrieve. " \
@@ -57,7 +57,7 @@ class Info < AbstractCommand
         switch "--eval-all",
                depends_on:  "--json",
                description: "Evaluate all available formulae and casks, whether installed or not, to print their " \
-                            "JSON. Implied if `HOMEBREW_EVAL_ALL` is set."
+                            "JSON. Implied if `$HOMEBREW_EVAL_ALL` is set."
         switch "--variations",
                depends_on:  "--json",
                description: "Include the variations hash in each formula's JSON output."

Library/Homebrew/cmd/install.rb

@@ -20,13 +20,13 @@ class InstallCmd < AbstractCommand
           Install a <formula> or <cask>. Additional options specific to a <formula> may be
           appended to the command.
 
-          Unless `HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
+          Unless `$HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
           outdated dependents and dependents with broken linkage, respectively.
 
-          Unless `HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for
+          Unless `$HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for
           the installed formulae or, every 30 days, for all formulae.
 
-          Unless `HOMEBREW_NO_INSTALL_UPGRADE` is set, `brew install` <formula> will upgrade <formula> if it
+          Unless `$HOMEBREW_NO_INSTALL_UPGRADE` is set, `brew install` <formula> will upgrade <formula> if it
           is already installed but outdated.
         EOS
         switch "-d", "--debug",

Library/Homebrew/cmd/nodenv-sync.rb

@@ -9,7 +9,7 @@ module Cmd
     class NodenvSync < AbstractCommand
       cmd_args do
         description <<~EOS
-          Create symlinks for Homebrew's installed NodeJS versions in `~/.nodenv/versions`.
+          Create symlinks for Homebrew's installed NodeJS versions in `${HOME}/.nodenv/versions`.
 
           Note that older version symlinks will also be created so e.g. NodeJS 19.1.0 will
           also be symlinked to 19.0.0.

Library/Homebrew/cmd/pyenv-sync.rb

@@ -9,7 +9,7 @@ module Cmd
     class PyenvSync < AbstractCommand
       cmd_args do
         description <<~EOS
-          Create symlinks for Homebrew's installed Python versions in `~/.pyenv/versions`.
+          Create symlinks for Homebrew's installed Python versions in `${HOME}/.pyenv/versions`.
 
           Note that older patch version symlinks will be created and linked to the minor
           version so e.g. Python 3.11.0 will also be symlinked to 3.11.3.

Library/Homebrew/cmd/rbenv-sync.rb

@@ -9,7 +9,7 @@ module Cmd
     class RbenvSync < AbstractCommand
       cmd_args do
         description <<~EOS
-          Create symlinks for Homebrew's installed Ruby versions in `~/.rbenv/versions`.
+          Create symlinks for Homebrew's installed Ruby versions in `${HOME}/.rbenv/versions`.
 
           Note that older version symlinks will also be created so e.g. Ruby 3.2.1 will
           also be symlinked to 3.2.0.

Library/Homebrew/cmd/readall.rb

@@ -25,7 +25,7 @@ class ReadallCmd < AbstractCommand
                description: "Syntax-check all of Homebrew's Ruby files (if no <tap> is passed)."
         switch "--eval-all",
                description: "Evaluate all available formulae and casks, whether installed or not. " \
-                            "Implied if `HOMEBREW_EVAL_ALL` is set."
+                            "Implied if `$HOMEBREW_EVAL_ALL` is set."
         switch "--no-simulate",
                description: "Don't simulate other system configurations when checking formulae and casks."
 
@@ -50,7 +50,7 @@ def run
 
           taps = if args.no_named?
             if !args.eval_all? && !Homebrew::EnvConfig.eval_all?
-              raise UsageError, "`brew readall` needs a tap or `--eval-all` passed or `HOMEBREW_EVAL_ALL` set!"
+              raise UsageError, "`brew readall` needs a tap or `--eval-all` passed or `$HOMEBREW_EVAL_ALL` set!"
             end
 
             Tap.installed

Library/Homebrew/cmd/reinstall.rb

@@ -22,10 +22,10 @@ class Reinstall < AbstractCommand
           Uninstall and then reinstall a <formula> or <cask> using the same options it was
           originally installed with, plus any appended options specific to a <formula>.
 
-          Unless `HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
+          Unless `$HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
           outdated dependents and dependents with broken linkage, respectively.
 
-          Unless `HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for the
+          Unless `$HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for the
           reinstalled formulae or, every 30 days, for all formulae.
         EOS
         switch "-d", "--debug",

Library/Homebrew/cmd/search.rb

@@ -40,7 +40,7 @@ class SearchCmd < AbstractCommand
         switch "--eval-all",
                depends_on:  "--desc",
                description: "Evaluate all available formulae and casks, whether installed or not, to search their " \
-                            "descriptions. Implied if `HOMEBREW_EVAL_ALL` is set."
+                            "descriptions. Implied if `$HOMEBREW_EVAL_ALL` is set."
         switch "--pull-request",
                description: "Search for GitHub pull requests containing <text>."
         switch "--open",
@@ -71,7 +71,7 @@ def run
 
         if args.desc?
           if !args.eval_all? && !Homebrew::EnvConfig.eval_all? && Homebrew::EnvConfig.no_install_from_api?
-            raise UsageError, "`brew search --desc` needs `--eval-all` passed or `HOMEBREW_EVAL_ALL` set!"
+            raise UsageError, "`brew search --desc` needs `--eval-all` passed or `$HOMEBREW_EVAL_ALL` set!"
           end
 
           Search.search_descriptions(string_or_regex, args)

Library/Homebrew/cmd/shellenv.rb

@@ -15,12 +15,15 @@ class Shellenv < AbstractCommand
 
           Print export statements. When run in a shell, this installation of Homebrew will be added to your `PATH`, `MANPATH`, and `INFOPATH`.
 
-          The variables `HOMEBREW_PREFIX`, `HOMEBREW_CELLAR` and `HOMEBREW_REPOSITORY` are also exported to avoid querying them multiple times.
-          To help guarantee idempotence, this command produces no output when Homebrew's `bin` and `sbin` directories are first and second
-          respectively in your `PATH`. Consider adding evaluation of this command's output to your dotfiles (e.g. `~/.bash_profile` or
-          `~/.zprofile` on macOS and `~/.bashrc` or `~/.zshrc` on Linux) with: `eval "$(brew shellenv)"`
+          The variables `$HOMEBREW_PREFIX`, `$HOMEBREW_CELLAR` and `$HOMEBREW_REPOSITORY` are also exported to avoid
+          querying them multiple times.
+          To help guarantee idempotence, this command produces no output when Homebrew's `bin` and `sbin` directories
+          are first and second respectively in your `PATH`. Consider adding evaluation of this command's output to
+          your dotfiles (e.g. `${HOME}/.bash_profile` or `${HOME}/.zprofile` on macOS and `${HOME}/.bashrc` or
+          `${HOME}/.zshrc` on Linux) with: `eval "$(brew shellenv)"`
 
-          The shell can be specified explicitly with a supported shell name parameter. Unknown shells will output POSIX exports.
+          The shell can be specified explicitly with a supported shell name parameter. Unknown shells will output
+          POSIX exports.
         EOS
         named_args :shell
       end

Library/Homebrew/cmd/tap.rb

@@ -41,7 +41,7 @@ class TapCmd < AbstractCommand
                description: "Migrate tapped formulae from symlink-based to directory-based structure."
         switch "--eval-all",
                description: "Evaluate all the formulae, casks and aliases in the new tap to check validity. " \
-                            "Implied if `HOMEBREW_EVAL_ALL` is set."
+                            "Implied if `$HOMEBREW_EVAL_ALL` is set."
         switch "-f", "--force",
                description: "Force install core taps even under API mode."
 

Library/Homebrew/cmd/upgrade.rb

@@ -19,10 +19,10 @@ class UpgradeCmd < AbstractCommand
           installed with, plus any appended brew formula options. If <cask> or <formula> are specified,
           upgrade only the given <cask> or <formula> kegs (unless they are pinned; see `pin`, `unpin`).
 
-          Unless `HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
+          Unless `$HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK` is set, `brew upgrade` or `brew reinstall` will be run for
           outdated dependents and dependents with broken linkage, respectively.
 
-          Unless `HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for the
+          Unless `$HOMEBREW_NO_INSTALL_CLEANUP` is set, `brew cleanup` will then be run for the
           upgraded formulae or, every 30 days, for all formulae.
         EOS
         switch "-d", "--debug",

Library/Homebrew/cmd/uses.rb

@@ -122,7 +122,7 @@ def intersection_of_dependents(use_runtime_dependents, used_formulae)
           all = args.eval_all?
 
           if !args.installed? && !(all || Homebrew::EnvConfig.eval_all?)
-            raise UsageError, "`brew uses` needs `--installed` or `--eval-all` passed or `HOMEBREW_EVAL_ALL` set!"
+            raise UsageError, "`brew uses` needs `--installed` or `--eval-all` passed or `$HOMEBREW_EVAL_ALL` set!"
           end
 
           if show_formulae_and_casks || args.formula?

Library/Homebrew/dev-cmd/livecheck.rb

@@ -14,7 +14,7 @@ class LivecheckCmd < AbstractCommand
           Check for newer versions of formulae and/or casks from upstream.
           If no formula or cask argument is passed, the list of formulae and
           casks to check is taken from `HOMEBREW_LIVECHECK_WATCHLIST` or
-          `~/.homebrew/livecheck_watchlist.txt`.
+          `${HOME}/.homebrew/livecheck_watchlist.txt`.
         EOS
         switch "--full-name",
                description: "Print formulae and casks with fully-qualified names."