virsh: More friendly err if no pool is specified for looking up a vol

There are 3 ways to lookup a volume, only virStorageVolLookupByName
needs pool object. So if no --pool is specified, it will tries to
get the volume via virStorageVolLookupByPath/virStorageVolLookupByKey.

But if all 3 ways fails, and no --pool is specified, a friendly
error might help the user get right way quickly.

diff --git a/tools/virsh.c b/tools/virsh.c
index 371346a825237cb7df65d058c83e462f305255ef..4b9e6624a9955c911838bd46be34be21a9c9865b 100644 (file)
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -14714,8 +14714,13 @@ vshCommandOptVolBy(vshControl *ctl, const vshCmd *cmd,
         vol = virStorageVolLookupByPath(ctl->conn, n);
     }
 
-    if (!vol)
-        vshError(ctl, _("failed to get vol '%s'"), n);
+    if (!vol) {
+        if (pool)
+            vshError(ctl, _("failed to get vol '%s'"), n);
+        else
+            vshError(ctl, _("failed to get vol '%s', specifying --pool "
+                            "might help"), n);
+    }
 
     if (pool)
         virStoragePoolFree(pool);