Automatically generate constants list for crew const (#5796)

* Automatically generate constants list for crew const

* Document code

bin/crew

@@ -402,45 +402,44 @@ def const(var)
     value = eval(var)
     puts "#{var}=#{value}"
   else
-    vars = [
-      'ARCH',
-      'ARCH_LIB',
-      'CHROMEOS_RELEASE',
-      'CURL',
-      'CREW_BREW_DIR',
-      'CREW_BUILD',
-      'CREW_CMAKE_LIBSUFFIX_OPTIONS',
-      'CREW_CMAKE_OPTIONS',
-      'CREW_CONFIG_PATH',
-      'CREW_DEST_DIR',
-      'CREW_DEST_HOME',
-      'CREW_DEST_LIB_PREFIX',
-      'CREW_DEST_MAN_PREFIX',
-      'CREW_DEST_PREFIX',
-      'CREW_LIB_PATH',
-      'CREW_LIB_PREFIX',
-      'CREW_LIB_SUFFIX',
-      'CREW_MAN_PREFIX',
-      'CREW_COMMON_FLAGS',
-      'CREW_COMMON_FNO_LTO_FLAGS',
-      'CREW_ENV_OPTIONS',
-      'CREW_MESON_FNO_LTO_OPTIONS',
-      'CREW_MESON_OPTIONS',
-      'CREW_META_PATH',
-      'CREW_NOT_COMPRESS',
-      'CREW_NOT_STRIP',
-      'CREW_NPROC',
-      'CREW_OPTIONS',
-      'CREW_PACKAGES_PATH',
-      'CREW_PREFIX',
-      'CREW_TGT',
-      'CREW_VERSION',
-      'HOME',
-      'LIBC_VERSION',
-      'USER'
+    @ruby_default_constants = %w[
+      ARGF
+      ARGV
+      CROSS_COMPILING
+      DOC
+      ENV
+      GC
+      IO
+      JSON
+      OpenSSL
+      Q
+      R
+      RUBY_COPYRIGHT
+      RUBY_DESCRIPTION
+      RUBY_ENGINE
+      RUBY_ENGINE_VERSION
+      RUBYGEMS_ACTIVATION_MONITOR
+      RUBY_PATCHLEVEL
+      RUBY_PLATFORM
+      RUBY_RELEASE_DATE
+      RUBY_REVISION
+      RUBY_VERSION
+      RubyVM
+      S
+      STDERR
+      STDIN
+      STDOUT
+      StringIO
+      TOPLEVEL_BINDING
+      URI
     ]
-    vars.each { |var|
-      value = eval(var)
+    # Get all constants
+    @constants = Module.constants.select {|e| e =~ /[[:upper:]]$/}
+    # Reject all constants which match the default list
+    @constants = @constants.map(&:to_s).reject{ |e| @ruby_default_constants.find{ |f| /\A#{e}\z/ =~ f }}
+    # Print a sorted list of the remaining constants used by crew.
+    @constants.sort.each { |var|
+      value = eval(var.to_s)
       puts "#{var}=#{value}"
     }
   end

lib/const.rb

 # Defines common constants used in different parts of crew
 
-CREW_VERSION = '1.10.3'
+CREW_VERSION = '1.10.4'
 
 ARCH_ACTUAL = `uname -m`.strip
 # This helps with virtualized builds on aarch64 machines