add setup.vsh, to make matching the installed SDL version easier for …

…users

Add a script to ease the post installation setup of SDL for end users.

setup.vsh

@@ -0,0 +1,29 @@
+import os
+
+os.chdir(os.dir(os.executable()))!
+
+res := os.execute('sdl2-config --version')
+if res.exit_code != 0 {
+	println('sdl2-config is missing')
+	exit(1)
+}
+system_version := res.output.trim_space()
+println('Your version is ${system_version}')
+
+remotes := os.execute('git branch -r --list')
+if remotes.exit_code != 0 {
+	println('git is missing')
+	exit(1)
+}
+supported_versions := remotes.output.split_into_lines().map(it.trim_space()).filter(it.starts_with('origin/2')).map(it.all_after('origin/'))
+println('The SDL module officially supports these versions of SDL:\n   ${supported_versions}')
+
+if system_version in supported_versions {
+	println('Setting up the repository to branch ${system_version} that exactly matches your system SDL version')
+	os.system('git checkout ${system_version}')
+	exit(0)
+}
+
+base_version := '${system_version.all_before_last('.')}.0'
+println('Setting up the repository to branch ${base_version}, that best matches the system SDL version: ${system_version} ...')
+os.system('git checkout ${base_version}')