;doc: update CLI usage texts

hledger/Hledger/Cli/Commands/Balance.txt

@@ -256,16 +256,29 @@ The idea of this is to be able to see a useful "complete" balance
 report, even when you don't have transactions in all of your declared
 accounts yet.
 
-Commodity layout
+Data layout
 
-With --layout, you can control how amounts with more than one commodity
-are displayed:
+With --layout, you can influence how amounts with more than one
+commodity are displayed (and a bit more), which in turn affects the
+layout of the report data:
 
--   --layout=wide[,WIDTH]: on a single line, possibly elided to the
-    specified width
--   --layout=tall: each commodity is displayed on a separate line
--   --layout=bare: amounts are displayed as bare numbers, with commodity
+-   --layout=wide[,WIDTH]: commodities are shown on a single line,
+    possibly elided to the specified width
+-   --layout=tall: each commodity is shown on a separate line
+-   --layout=bare: amounts are shown as bare numbers, with commodity
     symbols in a separate column
+-   --layout=tidy: data is normalised to tidy form, with one row per
+    data value (supported with CSV output only)
+
+These --layout values affect some but not all of the output formats, as
+shown:
+
+  -      txt   csv   html   json   sql
+  ------ ----- ----- ------ ------ -----
+  wide   Y     Y     Y             
+  tall   Y     Y     Y             
+  bare   Y     Y     Y             
+  tidy         Y                   
 
 Examples:
 
@@ -348,13 +361,44 @@ Examples:
     "total","VEA","36.00"
     "total","VHT","294.00"
 
-Here is how --layout currently affects the various output formats:
-
-  -      txt   csv   html   json   sql
-  ------ ----- ----- ------ ------ -----
-  wide   Y     Y     Y             
-  tall   Y     Y     Y             
-  bare   Y     Y     Y             
+-   Tidy layout produces normalised "tidy data", where every variable is
+    a column and each row represents a single data point (see
+    https://cran.r-project.org/web/packages/tidyr/vignettes/tidy-data.html).
+    This is the form of data most easily processed by other software.
+    Currently we support it with the CSV output format only:
+
+    $ hledger -f examples/bcexample.hledger bal assets:us:etrade -3 -O csv --layout=tidy -Y
+    "account","date","commodity","value"
+    "Assets:US:ETrade","2012","GLD","0"
+    "Assets:US:ETrade","2012","ITOT","10.00"
+    "Assets:US:ETrade","2012","USD","337.18"
+    "Assets:US:ETrade","2012","VEA","12.00"
+    "Assets:US:ETrade","2012","VHT","106.00"
+    "Assets:US:ETrade","2013","GLD","70.00"
+    "Assets:US:ETrade","2013","ITOT","18.00"
+    "Assets:US:ETrade","2013","USD","-98.12"
+    "Assets:US:ETrade","2013","VEA","10.00"
+    "Assets:US:ETrade","2013","VHT","18.00"
+    "Assets:US:ETrade","2014","GLD","0"
+    "Assets:US:ETrade","2014","ITOT","-11.00"
+    "Assets:US:ETrade","2014","USD","4881.44"
+    "Assets:US:ETrade","2014","VEA","14.00"
+    "Assets:US:ETrade","2014","VHT","170.00"
+    "total","2012","GLD","0"
+    "total","2012","ITOT","10.00"
+    "total","2012","USD","337.18"
+    "total","2012","VEA","12.00"
+    "total","2012","VHT","106.00"
+    "total","2013","GLD","70.00"
+    "total","2013","ITOT","18.00"
+    "total","2013","USD","-98.12"
+    "total","2013","VEA","10.00"
+    "total","2013","VHT","18.00"
+    "total","2014","GLD","0"
+    "total","2014","ITOT","-11.00"
+    "total","2014","USD","4881.44"
+    "total","2014","VEA","14.00"
+    "total","2014","VHT","170.00"
 
 Sorting by amount