virsh: blockresize: Introduce '--extend' flag

Use the new VIR_DOMAIN_BLOCK_RESIZE_EXTEND to prevent accidentally
shrinking a disk and thus destroying data.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tools/virsh-domain.c

@@ -3339,6 +3339,10 @@ static const vshCmdOptDef opts_blockresize[] = {
      .type = VSH_OT_BOOL,
      .help = N_("resize to capacity of source (block device)")
     },
+    {.name = "extend",
+     .type = VSH_OT_BOOL,
+     .help = N_("ensure that the new size is larger than actual capacity (prevent shrink)")
+    },
     {.name = NULL}
 };
 
@@ -3352,6 +3356,9 @@ cmdBlockresize(vshControl *ctl, const vshCmd *cmd)
 
     VSH_ALTERNATIVE_OPTIONS("size", "capacity");
 
+    if (vshCommandOptBool(cmd, "extend"))
+        flags |= VIR_DOMAIN_BLOCK_RESIZE_EXTEND;
+
     if (vshCommandOptString(ctl, cmd, "path", (const char **) &path) < 0)
         return false;