Auto-detect and link to Homebrew's readline

I thought this was not necessary, but a number of people had problems
when linking to OS X's "readline" (actually Editline wrapper):

- Some components of Pry wouldn't work
- Writing literal Unicode characters was not possible #379
- The compilation would downright fail in some cases #82 #461

Fixes #461

bin/ruby-build

@@ -398,6 +398,8 @@ build_package_standard() {
   local PACKAGE_MAKE_OPTS_ARRAY="${package_var_name}_MAKE_OPTS_ARRAY[@]"
   local PACKAGE_CFLAGS="${package_var_name}_CFLAGS"
 
+  [ "$package_var_name" = "RUBY" ] && use_homebrew_readline || true
+
   ( if [ "${CFLAGS+defined}" ] || [ "${!PACKAGE_CFLAGS+defined}" ]; then
       export CFLAGS="$CFLAGS ${!PACKAGE_CFLAGS}"
     fi
@@ -664,6 +666,17 @@ use_homebrew_yaml() {
   fi
 }
 
+use_homebrew_readline() {
+  if [[ "$RUBY_CONFIGURE_OPTS" != *--with-readline-dir=* ]]; then
+    local libdir="$(brew --prefix readline 2>/dev/null || true)"
+    if [ -d "$libdir" ]; then
+      package_option ruby configure --with-readline-dir="$libdir"
+    else
+      return 1
+    fi
+  fi
+}
+
 has_broken_mac_openssl() {
   [ "$(uname -s)" = "Darwin" ] &&
   [[ "$(openssl version 2>/dev/null || true)" = "OpenSSL 0.9.8"?* ]] &&

test/build.bats

@@ -77,7 +77,7 @@ OUT
   brew_libdir="$TMP/homebrew-yaml"
   mkdir -p "$brew_libdir"
 
-  stub brew "--prefix libyaml : echo '$brew_libdir'"
+  stub brew "--prefix libyaml : echo '$brew_libdir'" false
   stub_make_install
 
   install_fixture definitions/needs-yaml
@@ -92,6 +92,50 @@ make -j 2
 OUT
 }
 
+@test "readline is linked from Homebrew" {
+  cached_tarball "ruby-2.0.0"
+
+  readline_libdir="$TMP/homebrew-readline"
+  mkdir -p "$readline_libdir"
+
+  stub brew "--prefix readline : echo '$readline_libdir'"
+  stub_make_install
+
+  run_inline_definition <<DEF
+install_package "ruby-2.0.0" "http://ruby-lang.org/ruby/2.0/ruby-2.0.0.tar.gz"
+DEF
+  assert_success
+
+  unstub brew
+  unstub make
+
+  assert_build_log <<OUT
+ruby-2.0.0: --prefix=$INSTALL_ROOT --with-readline-dir=$readline_libdir
+make -j 2
+OUT
+}
+
+@test "readline is not linked from Homebrew when explicitly defined" {
+  cached_tarball "ruby-2.0.0"
+
+  stub brew
+  stub_make_install
+
+  export RUBY_CONFIGURE_OPTS='--with-readline-dir=/custom'
+  run_inline_definition <<DEF
+install_package "ruby-2.0.0" "http://ruby-lang.org/ruby/2.0/ruby-2.0.0.tar.gz"
+DEF
+  assert_success
+
+  unstub brew
+  unstub make
+
+  assert_build_log <<OUT
+ruby-2.0.0: --prefix=$INSTALL_ROOT --with-readline-dir=/custom
+make -j 2
+OUT
+}
+
 @test "number of CPU cores defaults to 2" {
   cached_tarball "ruby-2.0.0"