Change exit status (0: OK, 1: No match, 2: Error/Interrupted)

A la grep. Close #345

test/test_go.rb

@@ -780,11 +780,6 @@ class TestGoFZF < TestBase
     tmux.send_keys :Enter
   end
 
-  def test_invalid_term
-    tmux.send_keys "TERM=xxx fzf", :Enter
-    tmux.until { |lines| lines.any? { |l| l.include? 'Invalid $TERM: xxx' } }
-  end
-
   def test_with_nth
     writelines tempname, ['hello world ', 'byebye']
     assert_equal 'hello world ', `cat #{tempname} | #{FZF} -f"^he hehe" -x -n 2.. --with-nth 2,1,1`.chomp
@@ -801,6 +796,47 @@ class TestGoFZF < TestBase
     assert_equal src, `cat #{tempname} | #{FZF} -fhehe -x -n 2.. --with-nth 2,1,1 --no-ansi`.chomp
   end
 
+  def test_exit_0_exit_code
+    `echo foo | #{FZF} -q bar -0`
+    assert_equal 1, $?.exitstatus
+  end
+
+  def test_invalid_term
+    lines = `TERM=xxx #{FZF}`
+    assert_equal 2, $?.exitstatus
+    assert lines.include?('Invalid $TERM: xxx')
+  end
+
+  def test_invalid_option
+    lines = `#{FZF} --foobar 2>&1`
+    assert_equal 2, $?.exitstatus
+    assert lines.include?('unknown option: --foobar'), lines
+  end
+
+  def test_filter_exitstatus
+    # filter / streaming filter
+    ["", "--no-sort"].each do |opts|
+      assert `echo foo | #{FZF} -f foo #{opts}`.include?('foo')
+      assert_equal 0, $?.exitstatus
+
+      assert `echo foo | #{FZF} -f bar #{opts}`.empty?
+      assert_equal 1, $?.exitstatus
+    end
+  end
+
+  def test_exitstatus_empty
+    { '99' => '0', '999' => '1' }.each do |query, status|
+      tmux.send_keys "seq 100 | #{FZF} -q #{query}", :Enter
+      tmux.until { |lines| lines[-2] =~ %r{ [10]/100} }
+      tmux.send_keys :Enter
+
+      tmux.send_keys 'echo --\$?--'
+      tmux.until { |lines| lines.last.include? "echo --$?--" }
+      tmux.send_keys :Enter
+      tmux.until { |lines| lines.last.include? "--#{status}--" }
+    end
+  end
+
 private
   def writelines path, lines
     File.unlink path while File.exists? path