document new caching feature

infrastructure/man/man1/link-checksums.1

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: link-checksums.1,v 1.1 2010/09/13 11:31:42 espie Exp $
+.\"	$OpenBSD: link-checksums.1,v 1.2 2011/09/04 17:04:58 espie Exp $
 .\"
 .\" Copyright (c) 2010 Marc Espie <espie@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: September 13 2010 $
+.Dd $Mdocdate: September 4 2011 $
 .Dt LINK-CHECKSUMS 1
 .Os
 .Sh NAME
@@ -45,6 +45,22 @@ and creates hardlinks for each checksum algorithm in
 (by default, sha1 md5 rmd160 sha256),
 such as
 .Pa by_cipher/md5/8506fd205028a96c741e4037de6e3c42 .
+.Pp
+If
+.Ev CIPHER_CACHE
+is defined, it points to an
+.Nm sqlite3
+database
+that records timestamps from already checksummed files.
+In which case,
+.Nm
+is dependent on
+the packages
+.Nm sqlite3 ,
+.Nm p5-DBI ,
+and
+.Nm p5-DBD-SQLite
+being installed.
 .Sh SEE ALSO
 .Xr cksum 1 ,
 .Xr bsd.port.mk 5 ,