-When -o is specified, output files are created in that
-directory; otherwise in the current working directory.
+Each output file is numbered sequentially from 1, and uses the
+first line of the commit message (massaged for pathname safety)
+as the filename.
+
+When -o is specified, output files are created in <dir>; otherwise
+they are created in the current working directory. This option
+is ignored if --stdout is specified.