Merge pull request #18402 from Homebrew/brew-tap-speedup

Speed up `brew tap` for no arguments

Library/Homebrew/brew.sh

@@ -172,6 +172,12 @@ case "$@" in
     source "${HOMEBREW_LIBRARY}/Homebrew/list.sh"
     homebrew-list "$@" && exit 0
     ;;
+  # homebrew-tap only handles invocations with no arguments
+  tap)
+    source "${HOMEBREW_LIBRARY}/Homebrew/tap.sh"
+    homebrew-tap "$@"
+    exit 0
+    ;;
   # falls back to cmd/help.rb on a non-zero return
   help | --help | -h | --usage | "-?" | "")
     homebrew-help "$@" && exit 0

Library/Homebrew/tap.sh

@@ -0,0 +1,27 @@
+# Does the quickest output of brew tap possible for no arguments.
+# HOMEBREW_LIBRARY is set by bin/brew
+# shellcheck disable=SC2154
+
+normalise_tap_name() {
+  local directory="$1"
+  local user
+  local repository
+
+  user="$(tr '[:upper:]' '[:lower:]' <<<"${directory%%/*}")"
+  repository="$(tr '[:upper:]' '[:lower:]' <<<"${directory#*/}")"
+  repository="${repository#@(home|linux)brew-}"
+  echo "${user}/${repository}"
+}
+
+homebrew-tap() {
+  local taplib="${HOMEBREW_LIBRARY}/Taps"
+  (
+    shopt -s extglob
+
+    for directory in "${taplib}"/*/*
+    do
+      [[ -d "${directory}" ]] || continue
+      normalise_tap_name "${directory#"${taplib}"/}"
+    done | sort
+  )
+}