Incorporate ShellCheck into GitHub Action

.github/workflows/tests.yml

@@ -167,6 +167,14 @@ jobs:
         brew install vale
         vale docs/
 
+    - name: Run ShellCheck
+      run: |
+        brew install shellcheck
+        shellcheck --color bin/brew
+        ven='./Library/Homebrew/vendor/*'
+        taps='./Library/Taps/*'
+        find . -type f -iname "*\.sh" -not -path "$ven" -not -path "$taps" -exec shellcheck --color {} \;
+
     - name: Lint Dockerfile
       if: matrix.os == 'ubuntu-latest'
       run: |

Library/Homebrew/brew.sh

@@ -1,11 +1,12 @@
+#!/bin/bash
 # Force UTF-8 to avoid encoding issues for users with broken locale settings.
 if [[ "$(locale charmap 2>/dev/null)" != "UTF-8" ]]
 then
   export LC_ALL="en_US.UTF-8"
 fi
 
 # USER isn't always set so provide a fall back for `brew` and subprocesses.
-export USER=${USER:-`id -un`}
+export USER=${USER:-$(id -un)}
 
 # Where we store built products; a Cellar in HOMEBREW_PREFIX (often /usr/local
 # for bottles) unless there's already a Cellar in HOMEBREW_REPOSITORY.

Library/Homebrew/cmd/shellenv.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 #:  * `shellenv`
 #:
 #:  Print export statements. When run in a shell, this installation of Homebrew will be added to your `PATH`, `MANPATH`, and `INFOPATH`.

Library/Homebrew/cmd/update-reset.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 #:  * `update-reset` [<repository>]
 #:
 #:  Fetch and reset Homebrew and all tap repositories (or any specified <repository>) using `git`(1) to their latest `origin/master`.

Library/Homebrew/cmd/update.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 #:  * `update`, `up` [<options>]
 #:
 #:  Fetch the newest version of Homebrew and all formulae from GitHub using `git`(1) and perform any necessary migrations.

Library/Homebrew/cmd/vendor-install.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 #:  @hide_from_man_page
 #:  * `vendor-install` [<target>]
 #:

Library/Homebrew/utils/analytics.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 # Migrate analytics UUID to its new home in Homebrew repo's git config and
 # remove the legacy UUID file if detected.
 migrate-legacy-uuid-file() {

Library/Homebrew/utils/lock.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 # create a lock using `flock(2)`. A name is required as first argument.
 # the lock will be automatically unlocked when the shell process quits.
 # Noted due to the fixed FD, a shell process can only create one lock.

Library/Homebrew/utils/ruby.sh

@@ -1,3 +1,4 @@
+#!/bin/bash
 test_ruby () {
   if [[ ! -x $1 ]]
   then
@@ -44,7 +45,7 @@ If there's no Homebrew Portable Ruby available for your processor:
   then
     HOMEBREW_RUBY_PATH="$vendor_ruby_path"
     [[ -z "$HOMEBREW_MACOS" ]] && TERMINFO_DIRS="$vendor_ruby_terminfo"
-    if [[ $vendor_ruby_current_version != $vendor_ruby_latest_version ]]
+    if [[ $vendor_ruby_current_version != "$vendor_ruby_latest_version" ]]
     then
       if ! brew vendor-install ruby
       then

bin/brew

@@ -23,8 +23,8 @@ symlink_target_directory() {
 builtin enable compgen unset
 for cmd in $(builtin compgen -A builtin)
 do
-  builtin unset -f $cmd
-  builtin enable $cmd
+  builtin unset -f "$cmd"
+  builtin enable "$cmd"
 done
 unset cmd