Rewrite route with sane(r) approach ro targets

Simplify maintenance by moving list of valid_targets to a separate
function.  Both router and usage message are now consumers thereof.

This also changes format of the usage message.

src/include/mkit.sh

@@ -87,11 +87,34 @@ route() {
     #
     # Call correct function based on $1
     #
-    case $1 in
-        build|build_manpages|clean|dist|rpmstuff|install|release_?|uninstall|vbump_?)
-            $1
-            ;;
-        *)
-            echo "usage: $(basename "$0") build|clean|dist|rpmstuff|install|uninstall" >&2
-    esac
+    if valid_targets | grep -qwx "^$1";
+    then
+        "$1"
+    else
+        {
+            echo "usage: $(basename "$0") TARGET"
+            echo
+            echo "valid targets:"
+            valid_targets | sed 's/^/    /'
+        } >&2
+    fi
+}
+
+valid_targets() {
+    #
+    # List valid routes
+    #
+    echo build
+    echo build_manpages
+    echo clean
+    echo dist
+    echo install
+    echo release_x
+    echo release_y
+    echo release_z
+    echo rpmstuff
+    echo uninstall
+    echo vbump_x
+    echo vbump_y
+    echo vbump_z
 }