generate __version__.py during the buck build

Summary:
The chg code now always attempts to import __version__.py
Previously this was not generated during buck-based builds.  This updates the
buck build to generate a __version__.py file now.

Reviewed By: ryanmce

Differential Revision: D8601650

fbshipit-source-id: 59bd0605394feeabcc41766a7e55cbdd253f07ad

gen_version.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+# Copyright 2004-present Facebook. All Rights Reserved.
+import argparse
+import errno
+import hashlib
+import os
+import struct
+
+
+MAIN_VERSION = "4.4.2"
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--version", required=True)
+    ap.add_argument("--release", required=True)
+    ap.add_argument("--revision", required=True)
+    ap.add_argument("output_path")
+    args = ap.parse_args()
+
+    if args.version and args.release:
+        sub_version = "%s_%s_%s" % (args.version, args.release, args.revision[:8])
+    elif args.revision:
+        sub_version = args.revision[:8]
+    else:
+        # Buck does not pass in any build data info in dev builds
+        sub_version = "dev"
+
+    version = "%s_%s" % (MAIN_VERSION, sub_version)
+    versionb = version.encode("ascii")
+    versionhash = struct.unpack(">Q", hashlib.sha1(versionb).digest()[:8])[0]
+
+    contents = (
+        "# auto-generated by the build\n" 'version = "%s"\n' "versionhash = %s\n"
+    ) % (version, versionhash)
+
+    try:
+        output_dir = os.path.dirname(args.output_path)
+        os.makedirs(output_dir)
+    except OSError as ex:
+        if ex.errno != errno.EEXIST:
+            raise
+
+    with open(args.output_path, "w") as f:
+        f.write(contents)
+
+
+main()

tests/test-check-code.t

@@ -217,6 +217,7 @@ Prevent adding new files in the root directory accidentally.
   Makefile
   README.rst
   TARGETS
+  gen_version.py
   hg
   hgeditor
   hgweb.cgi