virsh: domain: Add --print-xml flag for command change-media

Allow printing the XML that would be used mostly for debugging purposes.

tools/virsh-domain.c

@@ -12274,6 +12274,10 @@ static const vshCmdOptDef opts_change_media[] = {
      .type = VSH_OT_BOOL,
      .help = N_("force media changing")
     },
+    {.name = "print-xml",
+     .type = VSH_OT_BOOL,
+     .help = N_("print XML document rather than change media")
+    },
     {.name = NULL}
 };
 
@@ -12354,12 +12358,17 @@ cmdChangeMedia(vshControl *ctl, const vshCmd *cmd)
     if (!(disk_xml = vshPrepareDiskXML(disk_node, source, path, prepare_type)))
         goto cleanup;
 
-    if (virDomainUpdateDeviceFlags(dom, disk_xml, flags) != 0) {
-        vshError(ctl, _("Failed to complete action %s on media"), action);
-        goto cleanup;
+    if (vshCommandOptBool(cmd, "print-xml")) {
+        vshPrint(ctl, "%s", disk_xml);
+    } else {
+        if (virDomainUpdateDeviceFlags(dom, disk_xml, flags) != 0) {
+            vshError(ctl, _("Failed to complete action %s on media"), action);
+            goto cleanup;
+        }
+
+        vshPrint(ctl, _("succeeded to complete action %s on media\n"), action);
     }
 
-    vshPrint(ctl, _("succeeded to complete action %s on media\n"), action);
     ret = true;
 
  cleanup:

tools/virsh.pod

@@ -2597,6 +2597,7 @@ expected.
 
 =item B<change-media> I<domain> I<path> [I<--eject>] [I<--insert>]
 [I<--update>] [I<source>] [I<--force>] [[I<--live>] [I<--config>] | [I<--current>]]
+[I<--print-xml>]
 
 Change media of CDROM or floppy drive. I<path> can be the fully-qualified path
 or the unique target name (<target dev='hdc'>) of the disk device. I<source>
@@ -2620,6 +2621,8 @@ the hypervisor's implementation.
 Both I<--live> and I<--config> flags may be given, but I<--current> is
 exclusive. If no flag is specified, behavior is different depending
 on hypervisor.
+If I<--print-xml> is specified, the XML that would be used to change media is
+printed instead of changing the media.
 
 =back