chore: Add initial version calculation script

Author: twpol

GetVersion.cmd

@@ -0,0 +1,26 @@
+@ECHO OFF
+SETLOCAL ENABLEEXTENSIONS ENABLEDELAYEDEXPANSION
+
+REM Parse command line.
+SET Mode=%~1
+
+REM Get product version.
+REM TODO!
+
+REM Get code revision.
+REM   For Subversion, this is a positive integer.
+REM   For Git, this is the stable version, new commits, and latest commit ID hyphenated.
+SET Revision=
+IF EXIST ".svn" (
+	FOR /F "usebackq tokens=1" %%R IN (`svn --non-interactive info --show-item revision .`) DO SET Revision=%%R
+)
+IF EXIST ".git" (
+	FOR /F "usebackq tokens=1" %%R IN (`git describe --first-parent --always`) DO SET Revision=%%R
+)
+IF "%Revision%" == "" (
+	>&2 ECHO WARNING: No Subversion or Git revision found.
+)
+
+REM Output version numbers.
+ECHO OpenRails_Version=%Version%
+ECHO OpenRails_Revision=%Revision%