reg: document --align-all (#1839)

hledger/Hledger/Cli/Commands/Aregister.md

@@ -48,6 +48,11 @@ Each `aregister` line item shows:
 Transactions making a net change of zero are not shown by default;
 add the `-E/--empty` flag to show them.
 
+For performance reasons, column widths are chosen based on the first 100 lines;
+this means unusually wide values in later lines can cause visual discontinuities
+as column widths are adjusted. If you want to ensure perfect alignment, 
+at the cost of more time and memory, use the `--align-all` flag.
+
 This command also supports the
 [output destination](hledger.html#output-destination) and
 [output format](hledger.html#output-format) options.

hledger/Hledger/Cli/Commands/Register.md

@@ -25,6 +25,11 @@ $ hledger register checking
 
 With --date2, it shows and sorts by secondary date instead.
 
+For performance reasons, column widths are chosen based on the first 100 lines;
+this means unusually wide values in later lines can cause visual discontinuities
+as column widths are adjusted. If you want to ensure perfect alignment, 
+at the cost of more time and memory, use the `--align-all` flag.
+
 The `--historical`/`-H` flag adds the balance from any undisplayed
 prior postings to the running total.  This is useful when you want to
 see only recent activity, with a historically accurate running balance: