The most recent release of Xmt is version 2.1.  The file xmt212.tar.gz
is a gzipped tar file that contains Xmt 2.1, patchlevel 2 (also known as
Xmt 2.1.2).

If you have an earlier release of Xmt 2.1, you can upgrade to patchlevel
2 by applying the patches in the files xmt_patches_210_to_211 and
xmt_patches_211_to_212.  You'll be able to upgrade to future patch
releases by a similar process.