doc: Clarify where ereport severity levels are defined

For a reader unfamiliar with the postgres code it might take some
grepping to find where elevels are defined. This adds a reference
to elog.h in the text like how SQLSTATE errorcodes are referenced
to errcodes.h on the same page.

Author: Kuwamura Masaki 
Discussion: https://postgr.es/m/CAMyC8qqp1UDA9zothnJ9CbUYByytwpALS3LkdZ6bs1w5kZw5Xg@mail.gmail.com

diff --git a/doc/src/sgml/sources.sgml b/doc/src/sgml/sources.sgml
index 514090d5a64b4c5293c31bf26fc4b686d97a5310..06d995e4b7616b692bdf9f70c03083b47d0760bf 100644 (file)
--- a/doc/src/sgml/sources.sgml
+++ b/doc/src/sgml/sources.sgml
@@ -105,7 +105,8 @@ less -x4
 
    
     There are two required elements for every message: a severity level
-    (ranging from DEBUG to PANIC) and a primary
+    (ranging from DEBUG to PANIC, defined
+    in src/include/utils/elog.h) and a primary
     message text.  In addition there are optional elements, the most
     common of which is an error identifier code that follows the SQL spec's
     SQLSTATE conventions.