Give build a --write-only-new option.

grit/tool/build_unittest.py

Index: grit/tool/build_unittest.py
===================================================================
--- grit/tool/build_unittest.py	(revision 182)
+++ grit/tool/build_unittest.py	(working copy)
@@ -245,6 +245,35 @@
         non_whitelisted_ids,
       )
 
+  def testWriteOnlyNew(self):
+    output_dir = tempfile.mkdtemp()
+    builder = build.RcBuilder()
+    class DummyOpts(object):
+      def __init__(self):
+        self.input = util.PathFromRoot('grit/testdata/substitute.grd')
+        self.verbose = False
+        self.extra_verbose = False
+    UNCHANGED = 10
+    header = os.path.join(output_dir, 'resource.h')
 
+    builder.Run(DummyOpts(), ['-o', output_dir])
+    self.failUnless(os.path.exists(header))
+    first_mtime = os.stat(header).st_mtime
+
+    os.utime(header, (UNCHANGED, UNCHANGED))
+    builder.Run(DummyOpts(), ['-o', output_dir, '--write-only-new', '0'])
+    self.failUnless(os.path.exists(header))
+    second_mtime = os.stat(header).st_mtime
+
+    os.utime(header, (UNCHANGED, UNCHANGED))
+    builder.Run(DummyOpts(), ['-o', output_dir, '--write-only-new', '1'])
+    self.failUnless(os.path.exists(header))
+    third_mtime = os.stat(header).st_mtime
+
+    self.assertTrue(abs(second_mtime - UNCHANGED) > 5)
+    self.assertTrue(abs(second_mtime - first_mtime) < 5)

[newt (away), 2014/12/04 22:45:22]

What's the purpose of this line? It seems only to be checking that the host
machine isn't extremely slow.

[Nico, 2014/12/04 22:47:49]

Yeah, I guess it's not very different from the line above it. I'll remove it.

+    self.assertTrue(abs(third_mtime - UNCHANGED) < 5)
+
+
 if __name__ == '__main__':
   unittest.main()