ENV/scm/git: rewrite in Bash (#496)

Library/ENV/scm/git

@@ -1,71 +1,120 @@
-#!/bin/sh
-# Make sure this shim uses the same Ruby interpreter that is used by Homebrew.
-unset RUBYLIB
-unset RUBYOPT
-if [ -z "$HOMEBREW_RUBY_PATH" ]
-then
-  echo "${0##*/}: The build tool has reset ENV; --env=std required." >&2
-  exit 1
-fi
-exec "$HOMEBREW_RUBY_PATH" -x "$0" "$@"
-#!/usr/bin/env ruby -W0
+#!/bin/bash
 
 # This script because we support $GIT, $HOMEBREW_SVN, etc., Xcode-only and
 # no Xcode/CLT configurations. Order is careful to be what the user would want.
 
-require "pathname"
+set +o posix
 
-SELF_REAL = Pathname.new(__FILE__).realpath
-F = File.basename(__FILE__).freeze
-D = File.expand_path(File.dirname(__FILE__)).freeze
+quiet_safe_cd() {
+  cd "$1" >/dev/null || { echo "Error: failed to cd to $1" >&2; exit 1; }
+}
 
-def executable?(file)
-  File.file?(file) && File.executable?(file)
-end
+realpath() {
+  local path="$1"
+  local dir
+  local base
+  local dest
 
-def exec(*args)
+  dir="$(quiet_safe_cd "${path%/*}/" && pwd -P)"
+  base="${path##*/}"
+  path="$dir/$base"
+
+  while [[ -L "$path" ]]
+  do
+    dest="$(readlink "$path")"
+    if [[ "$dest" = "/"* ]]
+    then
+      path="$dest"
+    else
+      path="$dir/$dest"
+    fi
+    dir="$(quiet_safe_cd "${path%/*}/" && pwd -P)"
+    base="${path##*/}"
+    path="$dir/$base"
+  done
+
+  echo "$path"
+}
+
+executable() {
+  local file="$1"
+  [[ -f "$file" && -x "$file" ]]
+}
+
+lowercase() {
+  echo "$1" | tr '[:upper:]' '[:lower:]'
+}
+
+safe_exec() {
+  local arg0="$1"
+  if ! executable "$arg0"
+  then
+    return
+  fi
   # prevent fork-bombs
-  arg0 = args.first
-  return if arg0 =~ /^#{F}/i || Pathname.new(arg0).realpath == SELF_REAL
-  if ARGV == %w[--homebrew=print-path]
-    puts arg0
+  if [[ "$(lowercase "$arg0")" = "$SCM_FILE" || "$(realpath "$arg0")" = "$SCM_REAL" ]]
+  then
+    return
+  fi
+  if [[ "$HOMEBREW" = "print-path" ]]
+  then
+    echo "$arg0"
     exit
-  end
-  super
-end
+  fi
+  exec "$@"
+}
 
-case F.downcase
-when "git" then %W[HOMEBREW_GIT GIT]
-when "svn" then %W[HOMEBREW_SVN]
-else []
-end.each do |key|
-  exec ENV[key], *ARGV if ENV[key] && executable?(ENV[key])
-end
+SCM_FILE="${0##*/}"
+SCM_DIR="$(quiet_safe_cd "${0%/*}/" && pwd -P)"
+SCM_REAL="$(realpath "$0")"
 
-brew_version = File.expand_path("#{D}/../../../bin/#{F}")
-exec brew_version, *ARGV if executable? brew_version
+if [[ "$1" = --homebrew=* ]]
+then
+  HOMEBREW="${1:11}"
+  shift
+fi
 
-`/usr/bin/which -a #{F} 2>/dev/null`.split("\n").each do |path|
-  exec path, *ARGV unless path == "/usr/bin/#{F}"
-end
+case "$(lowercase "$SCM_FILE")" in
+  git)
+    [[ -n "$HOMEBREW_GIT" ]] && safe_exec "$(which "$HOMEBREW_GIT")" "$@"
+    [[ -n "$GIT" ]] && safe_exec "$(which "$GIT")" "$@"
+    ;;
+  svn)
+    [[ -n "$HOMEBREW_SVN" ]] && safe_exec "$(which "$HOMEBREW_SVN")" "$@"
+    ;;
+esac
 
-popup_stub = false
-if executable? "/usr/bin/xcode-select"
+brew_version="$(quiet_safe_cd "$SCM_DIR/../../../bin" && pwd -P)/$SCM_FILE"
+safe_exec "$brew_version" "$@"
+
+IFS=$'\n'
+for path in $(/usr/bin/which -a "$SCM_FILE" 2>/dev/null)
+do
+  if [[ "$path" != "/usr/bin/$SCM_FILE" ]]
+  then
+    safe_exec "$path" "$@"
+  fi
+done
+
+if executable "/usr/bin/xcode-select"
+then
   # xcode-select will return empty on no Xcode/CLT configuration.
   #   /usr/bin/<tool> will be a popup stub under such configuration.
   # xcrun hangs if xcode-select is set to "/"
-  path = `/usr/bin/xcode-select -print-path 2>/dev/null`.chomp
-  popup_stub = path.empty?
-  if !popup_stub && path != "/"
-    path = `/usr/bin/xcrun -find #{F} 2>/dev/null`.chomp
-    exec path, *ARGV if executable? path
-  end
-end
+  xcode_path="$(/usr/bin/xcode-select -print-path 2>/dev/null)"
+  [[ -n "$xcode_path" ]] || popup_stub=1
+  if [[ -z "$popup_stub" && "$xcode_path" != "/" ]]
+  then
+    path="$(/usr/bin/xcrun -find "$SCM_FILE" 2>/dev/null)"
+    safe_exec "$path" "$@"
+  fi
+fi
 
-path = "/Applications/Xcode.app/Contents/Developer/usr/bin/#{F}"
-exec path, *ARGV if executable? path
+path="/Applications/Xcode.app/Contents/Developer/usr/bin/$SCM_FILE"
+safe_exec "$path" "$@"
 
-path = "/usr/bin/#{F}"
-exec path, *ARGV if !popup_stub && executable?(path)
+path="/usr/bin/$SCM_FILE"
+[[ -z "$popup_stub" ]] && safe_exec "$path" "$@"
 
-abort "You must: brew install #{F}"
+echo "You must: brew install $SCM_FILE" >&2
+exit 1