i.vi: red band not required and GUI section modified (#179)

Fixes https://trac.osgeo.org/grass/ticket/3932

imagery/i.vi/main.c

@@ -98,12 +98,6 @@ int main(int argc, char *argv[])
 			    "and some indices require additional bands.");
 
     /* Define the different options */
-    opt.red = G_define_standard_option(G_OPT_R_INPUT);
-    opt.red->key = "red";
-    opt.red->label =
-	_("Name of input red channel surface reflectance map");
-    opt.red->description = _("Range: [0.0;1.0]");
-
     opt.output = G_define_standard_option(G_OPT_R_OUTPUT);
 
     opt.viname = G_define_option();
@@ -137,13 +131,21 @@ int main(int argc, char *argv[])
     opt.viname->answer = "ndvi";
     opt.viname->key_desc = _("type");
 
+    opt.red = G_define_standard_option(G_OPT_R_INPUT);
+    opt.red->key = "red";
+    opt.red->required = NO;
+    opt.red->label =
+	_("Name of input red channel surface reflectance map");
+    opt.red->description = _("Range: [0.0;1.0]");
+    opt.red->guisection = _("Inputs");
+	
     opt.nir = G_define_standard_option(G_OPT_R_INPUT);
     opt.nir->key = "nir";
     opt.nir->required = NO;
     opt.nir->label =
 	_("Name of input nir channel surface reflectance map");
     opt.nir->description = _("Range: [0.0;1.0]");
-    opt.nir->guisection = _("Optional inputs");
+    opt.nir->guisection = _("Inputs");
 
     opt.green = G_define_standard_option(G_OPT_R_INPUT);
     opt.green->key = "green";
@@ -151,7 +153,7 @@ int main(int argc, char *argv[])
     opt.green->label =
 	_("Name of input green channel surface reflectance map");
     opt.green->description = _("Range: [0.0;1.0]");
-    opt.green->guisection = _("Optional inputs");
+    opt.green->guisection = _("Inputs");
 
     opt.blue = G_define_standard_option(G_OPT_R_INPUT);
     opt.blue->key = "blue";
@@ -159,7 +161,7 @@ int main(int argc, char *argv[])
     opt.blue->label =
 	_("Name of input blue channel surface reflectance map");
     opt.blue->description = _("Range: [0.0;1.0]");
-    opt.blue->guisection = _("Optional inputs");
+    opt.blue->guisection = _("Inputs");
 
     /* TODO: the naming is suboptimal as specific to Landsat-7 */
     opt.chan5 = G_define_standard_option(G_OPT_R_INPUT);
@@ -168,7 +170,7 @@ int main(int argc, char *argv[])
     opt.chan5->label =
 	_("Name of input 5th channel surface reflectance map");
     opt.chan5->description = _("Range: [0.0;1.0]");
-    opt.chan5->guisection = _("Optional inputs");
+    opt.chan5->guisection = _("Inputs");
 
     /* TODO: the naming is suboptimal as specific to Landsat-7 */
     opt.chan7 = G_define_standard_option(G_OPT_R_INPUT);
@@ -177,7 +179,7 @@ int main(int argc, char *argv[])
     opt.chan7->label =
 	_("Name of input 7th channel surface reflectance map");
     opt.chan7->description = _("Range: [0.0;1.0]");
-    opt.chan7->guisection = _("Optional inputs");
+    opt.chan7->guisection = _("Inputs");
 
     opt.sl_slope = G_define_option();
     opt.sl_slope->key = "soil_line_slope";