zpool import -t should not update cachefile

zpool import's -t parameter is intended for use with -R when operating
on pools that belong to other systems. Like -R, pools imported in this
way should not update the cachefile unless explicitly requested. The
initial implementation allowed the cachefile to be updated when -R was
not used. This went uncaught during testing because -R had implicitly
disabled use of the cachefile.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue openzfs#2417

cmd/zpool/zpool_main.c

@@ -2085,6 +2085,9 @@ zpool_do_import(int argc, char **argv)
 			break;
 		case 't':
 			flags |= ZFS_IMPORT_TEMP_NAME;
+			if (add_prop_list_default(zpool_prop_to_name(
+			    ZPOOL_PROP_CACHEFILE), "none", &props, B_TRUE))
+				goto error;
 			break;
 
 		case 'T':

man/man8/zpool.8

@@ -1474,7 +1474,7 @@ Specify the txg to use for rollback.  Implies \fB-FX\fR. For more details about
 .ad
 .sp .6
 .RS 4n
-Used with "\fBnewpool\fR". Specifies that "\fBnewpool\fR" is temporary. Temporary pool names last until export. Ensures that the original pool name will be used in all label updates and therefore is retained upon export.
+Used with "\fBnewpool\fR". Specifies that "\fBnewpool\fR" is temporary. Temporary pool names last until export. Ensures that the original pool name will be used in all label updates and therefore is retained upon export. Will also set -o cachefile=none when not explicitly specified.
 .RE
 
 .sp