Document the lager_truncation_size compile-time option

README.org

@@ -236,3 +236,18 @@
 #+BEGIN_EXAMPLE
   lager:trace_console([{pid, "<0.410.0>"}])
 #+END_EXAMPLE
+
+* Setting the truncation limit at compile-time
+  Lager defaults to truncating messages at 4096 bytes, you can alter this by
+  using the {lager_truncation_size, X} option. In rebar, you can add it to
+  erl_opts:
+
+#+BEGIN_EXAMPLE
+  {erl_opts, [{parse_transform, lager_transform}, {lager_truncation_size, 1024}]}.
+#+END_EXAMPLE
+
+  You can also pass it to erlc, if you prefer:
+
+#+BEGIN_EXAMPLE
+  erlc -pa lager/ebin +'{parse_transform, lager_transform}' +'{lager_truncation_size, 64}' file.erl
+l+END_EXAMPLE