diff --git a/Library/Homebrew/shims/scm/git b/Library/Homebrew/shims/scm/git
index 6b0382ad6e..4f397eb386 100755
--- a/Library/Homebrew/shims/scm/git
+++ b/Library/Homebrew/shims/scm/git
@@ -3,7 +3,8 @@
 # This script because we support $HOMEBREW_GIT, $HOMEBREW_SVN, etc., Xcode-only and
 # no Xcode/CLT configurations. Order is careful to be what the user would want.
 
-if [ -z "$HOMEBREW_LIBRARY" ]
+# shellcheck disable=SC2154
+if [ -z "${HOMEBREW_LIBRARY}" ]
 then
   echo "${0##*/}: This shim is internal and must be run via brew." >&2
   exit 1
@@ -11,27 +12,28 @@ fi
 
 # Don't need shellcheck to follow the `source`.
 # shellcheck disable=SC1090
-source "$HOMEBREW_LIBRARY/Homebrew/shims/utils.sh"
+source "${HOMEBREW_LIBRARY}/Homebrew/shims/utils.sh"
 
-case "$(lowercase "$SHIM_FILE")" in
+# shellcheck disable=SC2249
+case "$(lowercase "${SHIM_FILE}")" in
   git)
-    if [[ -n "$HOMEBREW_GIT" && "$HOMEBREW_GIT" != git ]]
+    if [[ -n "${HOMEBREW_GIT}" && "${HOMEBREW_GIT}" != git ]]
     then
-      safe_exec "$(type -P "$HOMEBREW_GIT")" "$@"
+      safe_exec "$(type -P "${HOMEBREW_GIT}")" "$@"
     fi
     ;;
   svn)
-    if [[ -n "$HOMEBREW_SVN" && "$HOMEBREW_SVN" != svn ]]
+    if [[ -n "${HOMEBREW_SVN}" && "${HOMEBREW_SVN}" != svn ]]
     then
-      safe_exec "$(type -P "$HOMEBREW_SVN")" "$@"
+      safe_exec "$(type -P "${HOMEBREW_SVN}")" "$@"
     fi
     ;;
 esac
 
-brew_prefix_version="$HOMEBREW_PREFIX/bin/$SHIM_FILE"
-safe_exec "$brew_prefix_version" "$@"
+brew_prefix_version="${HOMEBREW_PREFIX}/bin/${SHIM_FILE}"
+safe_exec "${brew_prefix_version}" "$@"
 
-try_exec_non_system "$SHIM_FILE" "$@"
+try_exec_non_system "${SHIM_FILE}" "$@"
 
 if executable "/usr/bin/xcode-select"
 then
@@ -39,28 +41,28 @@ then
   #   /usr/bin/<tool> will be a popup stub under such configuration.
   # xcrun hangs if xcode-select is set to "/"
   xcode_path="$(/usr/bin/xcode-select -print-path 2>/dev/null)"
-  if [[ -z "$xcode_path" ]]
+  if [[ -z "${xcode_path}" ]]
   then
-    if [[ "$HOMEBREW_MACOS_VERSION_NUMERIC" -ge "100900" ]]
+    if [[ "${HOMEBREW_MACOS_VERSION_NUMERIC}" -ge "100900" ]]
     then
       popup_stub=1
     fi
   fi
-  if [[ -z "$popup_stub" && "$xcode_path" != "/" ]]
+  if [[ -z "${popup_stub}" && "${xcode_path}" != "/" ]]
   then
-    path="$(/usr/bin/xcrun -find "$SHIM_FILE" 2>/dev/null)"
-    safe_exec "$path" "$@"
+    path="$(/usr/bin/xcrun -find "${SHIM_FILE}" 2>/dev/null)"
+    safe_exec "${path}" "$@"
   fi
 fi
 
-path="/Applications/Xcode.app/Contents/Developer/usr/bin/$SHIM_FILE"
-safe_exec "$path" "$@"
+path="/Applications/Xcode.app/Contents/Developer/usr/bin/${SHIM_FILE}"
+safe_exec "${path}" "$@"
 
-if [[ -z "$popup_stub" && "$HOMEBREW_MACOS_VERSION_NUMERIC" -lt "101500" ]]
+if [[ -z "${popup_stub}" && "${HOMEBREW_MACOS_VERSION_NUMERIC}" -lt "101500" ]]
 then
-  path="/usr/bin/$SHIM_FILE"
-  safe_exec "$path" "$@"
+  path="/usr/bin/${SHIM_FILE}"
+  safe_exec "${path}" "$@"
 fi
 
-echo "You must: brew install $SHIM_FILE" >&2
+echo "You must: brew install ${SHIM_FILE}" >&2
 exit 1