generator: Add new virt-customize --tar-in operation

Using 'virt-customize --tar-in some.tar:/dir -a disk.img' will unpack
'some.tar' into '/dir' in the guest.  Note that this will not work for
compressed tar files as written since the underlying guestfs_tar_in
function requires the compression type to be set explicitly and
defaults to no compression (it does not auto-detect or default to
compression).

(cherry picked from commit b5f7b0ec18)

generator/customize.ml

@@ -510,6 +510,18 @@ You can have multiple I<--ssh-inject> options, for different users
 and also for more keys for each user."
   };
 
+  { op_name = "tar-in";
+    op_type = StringPair "TARFILE:REMOTEDIR";
+    op_discrim = "`TarIn";
+    op_shortdesc = "Copy local files or directories from a tarball into image";
+    op_pod_longdesc = "\
+Copy local files or directories from a local tar file
+called C<TARFILE> into the disk image, placing them in the
+directory C<REMOTEDIR> (which must exist).  Note that
+the tar file must be uncompressed (F<.tar.gz> files will not work
+here)";
+  };
+
   { op_name = "timezone";
     op_type = String "TIMEZONE";
     op_discrim = "`Timezone";