Filter kati output to collapse verbose messages

1. Collapses the "including .../Android.mk ..." lines like ninja does,
so that we overwrite the last line if there wasn't anything else to
print.
2. Strips ansi control codes so that log files don't include unreadable
characters.

Test: m -j
Test: m -j | tee output.log   (with colored output)
Change-Id: Ib18437f6f9d37084360097a9d586800c833072c5
diff --git a/ui/build/util_test.go b/ui/build/util_test.go
new file mode 100644
index 0000000..e85eada
--- /dev/null
+++ b/ui/build/util_test.go
@@ -0,0 +1,62 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build
+
+import "testing"
+
+func TestStripAnsiEscapes(t *testing.T) {
+	testcases := []struct {
+		input  string
+		output string
+	}{
+		{
+			"",
+			"",
+		},
+		{
+			"This is a test",
+			"This is a test",
+		},
+		{
+			"interrupted: \x1b[12",
+			"interrupted: ",
+		},
+		{
+			"other \x1bescape \x1b",
+			"other \x1bescape \x1b",
+		},
+		{ // from pretty-error macro
+			"\x1b[1mart/Android.mk: \x1b[31merror:\x1b[0m\x1b[1m art: test error \x1b[0m",
+			"art/Android.mk: error: art: test error ",
+		},
+		{ // from envsetup.sh make wrapper
+			"\x1b[0;31m#### make failed to build some targets (2 seconds) ####\x1b[00m",
+			"#### make failed to build some targets (2 seconds) ####",
+		},
+		{ // from clang (via ninja testcase)
+			"\x1b[1maffixmgr.cxx:286:15: \x1b[0m\x1b[0;1;35mwarning: \x1b[0m\x1b[1musing the result... [-Wparentheses]\x1b[0m",
+			"affixmgr.cxx:286:15: warning: using the result... [-Wparentheses]",
+		},
+	}
+	for _, tc := range testcases {
+		got := string(stripAnsiEscapes([]byte(tc.input)))
+		if got != tc.output {
+			t.Errorf("output strings didn't match\n"+
+				"input: %#v\n"+
+				" want: %#v\n"+
+				"  got: %#v", tc.input, tc.output, got)
+		}
+	}
+}