Improve documentation of interval-related args.

Minor rewording of the help text for the --unit-interval option and
a new sentence which explains that the total number of snapshots
doubles if --num-intervals is increased by one.

diff --git a/dss.ggo b/dss.ggo
index 68b7a7aded9250e56e2216e8c21ea391565dec53..8a3d304d6fcef2c1c1e9bf41c2acfc539bd2824e 100644 (file)
--- a/dss.ggo
+++ b/dss.ggo
@@ -275,22 +275,21 @@ int typestr="days"
 default="4"
 optional
 details="
-       dss snapshot aging is implemented in terms of intervals. There
-       are two command line options related to intervals: the
-       duration u of a \"unit\" interval and the number n of those
-       unit intervals.
-
-       dss removes any snapshots older than n times u and tries to
-       keep 2^(n - k - 1) snapshots in interval k, where the interval
-       number k counts from zero, zero being the most recent unit
-       interval.
-
-       In other words, the oldest snapshot will at most be u * n days
-       (= 20 days if default values are used) old.  Moreover, there
-       are at most 2^n - 1 snapshots in total (i. e. 31 by default).
-       Observe that you have to create at least 2^(n - 1) snapshots
-       each interval for this to work out because that is the number
-       of snapshots in interval zero.
+       Snapshot aging is implemented in terms of intervals. There are two
+       command line options related to intervals: the duration u of a unit
+       interval and the number of unit intervals, denoted n below.
+
+       dss removes snapshots older than n times u and tries to keep 2^(n -
+       k - 1) snapshots in interval k, where the interval number k counts
+       from zero to n - 1, with zero being the most recent unit interval.
+
+       Hence the oldest snapshot will at most be u * n days old (4 days *
+       5 intervals = 20 days, if default values are used). Moreover, there
+       are at most 2^n - 1 snapshots in total (2^5 - 1 = 31 by default). Note
+       that for this to work out your system must be fast enough to create at
+       least 2^(n - 1) snapshots per unit interval (16 snapshots in 4 days =
+       one snapshot in 6 hours), because this is the number of snapshots in
+       interval zero.
 "
 
 option "num-intervals" n
@@ -299,6 +298,10 @@ option "num-intervals" n
 int typestr="num"
 default="5"
 optional
+details="
+       Note that increasing this number by one doubles the total number of
+       snapshots. See the documentation of --unit-interval above.
+"
 
 ###############
 section "Hooks"