qbsp: add docs for -convert option

man/qbsp.1

@@ -82,6 +82,10 @@ Generate a hexen2 bsp.
 Write only placeholder textures, to depend upon replacements.
 .IP "\fB\-omitdetail\fP"
 Detail brushes are omitted from the compile.
+.IP "\fB\-convert <fmt>\fP"
+Convert a .MAP to a different .MAP format. fmt can be: quake, quake2, valve, bp (brush primitives).
+Conversions to "quake" or "quake2" format may not be able to match the texture alignment in the source map, other conversions are lossless.
+The converted map is saved to <source map name>-<fmt>.map.
 
 .SH "SPECIAL TEXTURE NAMES"
 .PP

qbsp/qbsp.cc

@@ -634,6 +634,7 @@ PrintOptions(void)
            "   -epsilon [n]    Customize ON_EPSILON (default 0.0001)\n"
            "   -objexport      Export the map file as an .OBJ model after the CSG phase\n"
            "   -omitdetail     Detail brushes are omitted from the compile\n"
+           "   -convert <fmt>  Convert a .MAP to a different .MAP format. fmt can be: quake, quake2, valve, bp (brush primitives).\n"
            "   sourcefile      .MAP file to process\n"
            "   destfile        .BSP file to output\n");
 
@@ -827,7 +828,7 @@ ParseOptions(char *szOptions)
                 } else if (!Q_strcasecmp(szTok2, "bp")) {
                     options.convertMapFormat = conversion_t::bp;
                 } else {
-                    Error("Invalid argument to option %s", szTok);
+                    Error("'-convert' requires one of: quake,quake2,valve,bp");
                 }
                 
                 options.fConvertMapFormat = true;