freebsd-update.8: Note availability of updates for ALPHA, BETA, and RC

While here, restructure the section about the binary updates
availability.

MFC after:	1 week

1 files changed, 31 insertions, 11 deletions

diff --git a/usr.sbin/freebsd-update/freebsd-update.8 b/usr.sbin/freebsd-update/freebsd-update.8
index de4b5b4a4c0b..6d7fc792c6f1 100644
--- a/usr.sbin/freebsd-update/freebsd-update.8
+++ b/usr.sbin/freebsd-update/freebsd-update.8
@@ -52,22 +52,42 @@ tool is used to fetch, install, and rollback binary
 updates to the
 .Fx
 base system.
-Note that updates are only available if they are being built for the
+.Sh BINARY UPDATES AVAILABILITY
+Binary updates are not available for every single
 .Fx
-release and architecture being used; in particular, the
+version and architecture.
+.Pp
+In general, binary updates are available for ALPHA, BETA, RC, and RELEASE
+versions of
+.Fx ,
+e.g.:
+.Bl -item -offset indent -compact
+.It
+.Fx 13.1-ALPHA3
+.It
+.Fx 13.1-BETA2
+.It
+.Fx 13.1-RC1
+.It
+.Fx 13.1-RELEASE
+.El
+They are not available for branches such as PRERELEASE, STABLE, and CURRENT,
+e.g.:
+.Bl -item -offset indent -compact
+.It
+.Fx 13.0-PRERELEASE
+.It
+.Fx 13.1-STABLE
+.It
+.Fx 14.0-CURRENT
+.El
+.Pp
+In particular, the
 .Fx
 Security Team only builds updates for releases shipped in binary form
 by the
 .Fx
-Release Engineering Team, e.g.,
-.Fx
-11.2-RELEASE and
-.Fx
-12.0-RELEASE, but not
-.Fx
-11.2-STABLE or
-.Fx
-13.0-CURRENT.
+Release Engineering Team.
 .Sh OPTIONS
 The following options are supported:
 .Bl -tag -width "-r newrelease"