fish: Make type == drv_N field private to guestfish.

The -N option / drv_N type only makes sense when we are compiling
guestfish, and just serves to complicate non-guestfish code.

df/main.c

@@ -325,7 +325,6 @@ single_drive_display_name (struct drv *drvs)
   case drv_d:
     name = drvs->d.guest;
     break;
-  case drv_N:
   default:
     abort ();
   }

fish/Makefile.am

@@ -120,6 +120,7 @@ cmds-gperf.c: cmds-gperf.gperf
 	mv $@-t $@
 
 guestfish_CFLAGS = \
+	-DCOMPILING_GUESTFISH=1 \
 	-DGUESTFS_WARN_DEPRECATED=1 \
 	-I$(top_srcdir)/src -I$(top_builddir)/src \
 	-I$(top_srcdir)/fish -I$(top_builddir)/fish \

fish/options.c

@@ -79,6 +79,7 @@ add_drives (struct drv *drv, char next_drive)
       next_drive += r;
       break;
 
+#if COMPILING_GUESTFISH
     case drv_N:
       /* guestfs_add_drive (ie. autodetecting) should be safe here
        * since we have just created the prepared disk.  At the moment
@@ -93,6 +94,7 @@ add_drives (struct drv *drv, char next_drive)
       drv->nr_drives = 1;
       next_drive++;
       break;
+#endif
 
     default: /* keep GCC happy */
       abort ();
@@ -181,10 +183,12 @@ free_drives (struct drv *drv)
   switch (drv->type) {
   case drv_a: /* a.filename and a.format are optargs, don't free them */ break;
   case drv_d: /* d.filename is optarg, don't free it */ break;
+#if COMPILING_GUESTFISH
   case drv_N:
     free (drv->N.filename);
     drv->N.data_free (drv->N.data);
     break;
+#endif
   default: ;                    /* keep GCC happy */
   }
   free (drv);

fish/options.h

@@ -80,7 +80,13 @@ struct drv {
                     */
   int nr_drives;   /* number of drives for this guest */
 
-  enum { drv_a, drv_d, drv_N } type;
+  enum {
+    drv_a,                      /* -a option */
+    drv_d,                      /* -d option */
+#if COMPILING_GUESTFISH
+    drv_N,                      /* -N option (guestfish only) */
+#endif
+  } type;
   union {
     struct {
       char *filename;       /* disk filename */