[feaLib] add __main__.py so one can call fonttools feaLib

This is the same as Snippets/apply-feature-file.py

Fixes #569

Lib/fontTools/feaLib/__main__.py

@@ -0,0 +1,42 @@
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+from fontTools.ttLib import TTFont
+from fontTools.feaLib.builder import addOpenTypeFeatures
+from fontTools import configLogger
+from fontTools.misc.cliTools import makeOutputFileName
+import sys
+import argparse
+import logging
+
+
+log = logging.getLogger("fontTools.feaLib")
+
+
+def main(args=None):
+    parser = argparse.ArgumentParser(
+        description="Use fontTools to compile OpenType feature files (*.fea).")
+    parser.add_argument(
+        "input_fea", metavar="FEATURES", help="Path to the feature file")
+    parser.add_argument(
+        "input_font", metavar="INPUT_FONT", help="Path to the input font")
+    parser.add_argument(
+        "-o", "--output", dest="output_font", metavar="OUTPUT_FONT",
+        help="Path to the output font.")
+    parser.add_argument(
+        "-v", "--verbose", help="increase the logger verbosity. Multiple -v "
+        "options are allowed.", action="count", default=0)
+    options = parser.parse_args(args)
+
+    levels = ["WARNING", "INFO", "DEBUG"]
+    configLogger(level=levels[min(len(levels) - 1, options.verbose)])
+
+    output_font = options.output_font or makeOutputFileName(options.input_font)
+    log.info("Compiling features to '%s'" % (output_font))
+
+    font = TTFont(options.input_font)
+    addOpenTypeFeatures(font, options.input_fea)
+    font.save(output_font)
+
+
+if __name__ == '__main__':
+    sys.exit(main())