Add --black for terminals incapable of use_default_colors

See the discussion in #18.

Use --black option to use black background regardless of the default
background color of the terminal. Also, this option can be used to fix
rendering issues on terminals that don't support use_default_colors (man
3 default_colors). Depending on the terminal, use_default_colors may or
may not succeed, but the Ruby version of it always returns nil, it's
currently not possible to automatically enable this option.

README.md

@@ -59,6 +59,7 @@ usage: fzf [options]
     +i                   Case-sensitive match
     +c, --no-color       Disable colors
     +2, --no-256         Disable 256-color
+        --black          Use black background
         --no-mouse       Disable mouse
 
   Environment variables

fzf

@@ -7,7 +7,7 @@
 #  / __/ / /_/ __/
 # /_/   /___/_/    Fuzzy finder for your shell
 #
-# Version: 0.8.0 (March 8, 2014)
+# Version: 0.8.1 (March 9, 2014)
 #
 # Author:  Junegunn Choi
 # URL:     https://github.com/junegunn/fzf
@@ -50,7 +50,7 @@ end
 
 class FZF
   C = Curses
-  attr_reader :rxflag, :sort, :color, :ansi256, :mouse, :multi, :query, :filter, :extended
+  attr_reader :rxflag, :sort, :color, :black, :ansi256, :mouse, :multi, :query, :filter, :extended
 
   class AtomicVar
     def initialize value
@@ -78,6 +78,7 @@ class FZF
     @sort     = ENV.fetch('FZF_DEFAULT_SORT', 1000).to_i
     @color    = true
     @ansi256  = true
+    @black    = false
     @multi    = false
     @mouse    = true
     @extended = nil
@@ -104,6 +105,8 @@ class FZF
       when '+c', '--no-color'    then @color    = false
       when '-2', '--256'         then @ansi256  = true
       when '+2', '--no-256'      then @ansi256  = false
+      when       '--black'       then @black    = true
+      when       '--no-black'    then @black    = false
       when       '--mouse'       then @mouse    = true
       when       '--no-mouse'    then @mouse    = false
       when '+s', '--no-sort'     then @sort     = nil
@@ -211,6 +214,7 @@ class FZF
     +i                   Case-sensitive match
     +c, --no-color       Disable colors
     +2, --no-256         Disable 256-color
+        --black          Use black background
         --no-mouse       Disable mouse
 
   Environment variables
@@ -517,7 +521,7 @@ class FZF
     C.mousemask C::ALL_MOUSE_EVENTS if @mouse
     C.start_color
     dbg =
-      if C.respond_to?(:use_default_colors)
+      if !@black && C.respond_to?(:use_default_colors)
         C.use_default_colors
         -1
       else

fzf.gemspec

@@ -1,7 +1,7 @@
 # coding: utf-8
 Gem::Specification.new do |spec|
   spec.name          = 'fzf'
-  spec.version       = '0.8.0'
+  spec.version       = '0.8.1'
   spec.authors       = ['Junegunn Choi']
   spec.email         = ['junegunn.c@gmail.com']
   spec.description   = %q{Fuzzy finder for your shell}

test/test_fzf.rb

@@ -28,7 +28,7 @@ class TestFZF < MiniTest::Unit::TestCase
     fzf = FZF.new []
     assert_equal 20000, fzf.sort
 
-    ENV['FZF_DEFAULT_OPTS'] = '-x -m -s 10000 -q "  hello  world  " +c +2 --no-mouse -f "goodbye world"'
+    ENV['FZF_DEFAULT_OPTS'] = '-x -m -s 10000 -q "  hello  world  " +c +2 --no-mouse -f "goodbye world" --black'
     fzf = FZF.new []
     assert_equal 10000,   fzf.sort
     assert_equal '  hello  world  ',
@@ -39,6 +39,7 @@ class TestFZF < MiniTest::Unit::TestCase
     assert_equal true,    fzf.multi
     assert_equal false,   fzf.color
     assert_equal false,   fzf.ansi256
+    assert_equal true,    fzf.black
     assert_equal false,   fzf.mouse
   end
 
@@ -50,6 +51,7 @@ class TestFZF < MiniTest::Unit::TestCase
     assert_equal true,    fzf.multi
     assert_equal false,   fzf.color
     assert_equal false,   fzf.ansi256
+    assert_equal false,   fzf.black
     assert_equal false,   fzf.mouse
     assert_equal 0,       fzf.rxflag
     assert_equal 'hello', fzf.query.get
@@ -57,12 +59,13 @@ class TestFZF < MiniTest::Unit::TestCase
     assert_equal :exact,  fzf.extended
 
     fzf = FZF.new %w[--sort=2000 --no-color --multi +i --query hello
-                     --filter a --filter b --no-256
+                     --filter a --filter b --no-256 --black
                      --no-sort -i --color --no-multi --256]
     assert_equal nil,     fzf.sort
     assert_equal false,   fzf.multi
     assert_equal true,    fzf.color
     assert_equal true,    fzf.ansi256
+    assert_equal true,    fzf.black
     assert_equal true,    fzf.mouse
     assert_equal 1,       fzf.rxflag
     assert_equal 'b',     fzf.filter
@@ -82,11 +85,12 @@ class TestFZF < MiniTest::Unit::TestCase
 
     # Left-to-right
     fzf = FZF.new %w[-s 2000 +c -m +i -qhello -x -fgoodbye +2
-                     -s 3000 -c +m -i -q world +x -fworld -2]
+                     -s 3000 -c +m -i -q world +x -fworld -2 --black --no-black]
     assert_equal 3000,    fzf.sort
     assert_equal false,   fzf.multi
     assert_equal true,    fzf.color
     assert_equal true,    fzf.ansi256
+    assert_equal false,   fzf.black
     assert_equal 1,       fzf.rxflag
     assert_equal 'world', fzf.query.get
     assert_equal 'world', fzf.filter