Auto-generate v8 version based on tags.

tools/push-to-trunk/generate_version.py

Index: tools/push-to-trunk/generate_version.py
diff --git a/tools/push-to-trunk/generate_version.py b/tools/push-to-trunk/generate_version.py
index b4a0221eae5c10224a18d79bf8067ca3df958177..4f0ba501783fc87dcdc21b32f2b746d3a5f2b106 100755
--- a/tools/push-to-trunk/generate_version.py
+++ b/tools/push-to-trunk/generate_version.py
@@ -19,6 +19,12 @@ CWD = os.path.abspath(
 VERSION_CC = os.path.join(CWD, "src", "version.cc")
 
 def main():
+  if len(sys.argv) != 2:
+    print "Error: Specify the output file path for version.cc"
+    return 1
+  version_out = sys.argv[1]
+  assert os.path.exists(os.path.dirname(version_out))
+
   tag = subprocess.check_output(
       "git describe --tags",
       shell=True,
@@ -63,7 +69,7 @@ def main():
       if line.startswith("#define %s" % definition):
         line =  re.sub("\d+$", substitute, line)
     output.append(line)
-  with open(VERSION_CC, "w") as f:
+  with open(version_out, "w") as f:
     f.write("\n".join(output))
 
   # Log what was done.