Doc: clarify description of regexp fields in pg_ident.conf.

The grammar was a little shaky and confusing here, so word-smith it
a bit.  Also, adjust the comments in pg_ident.conf.sample to use the
same terminology as the SGML docs, in particular "DATABASE-USERNAME"
not "PG-USERNAME".

Back-patch appropriate subsets.  I did not risk changing
pg_ident.conf.sample in released branches, but it still seems OK
to change it in v18.

Reported-by: Alexey Shishkin <[email protected]>
Author: Tom Lane <[email protected]>
Reviewed-by: David G. Johnston <[email protected]>
Discussion: https://postgr.es/m/175206279327.3157504.12519088928605422253@wrigleys.postgresql.org
Backpatch-through: 13

diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
index 9e22a5b403edf396364cf43b82365322fe58b8a6..fd257bfa853aedee569e6fe8f57ed7767e9ca046 100644 (file)
--- a/doc/src/sgml/client-auth.sgml
+++ b/doc/src/sgml/client-auth.sgml
@@ -864,8 +864,9 @@ local   db1,db2,@demodbs  all                                   md5
    the remainder of the field is treated as a regular expression.
    (See <xref linkend="posix-syntax-details"/> for details of
    <productname>PostgreSQL</productname>'s regular expression syntax.)  The regular
-   expression can include a single capture, or parenthesized subexpression,
-   which can then be referenced in the <replaceable>database-username</replaceable>
+   expression can include a single capture, or parenthesized subexpression.
+   The portion of the system user name that matched the capture can then
+   be referenced in the <replaceable>database-username</replaceable>
    field as <literal>\1</literal> (backslash-one).  This allows the mapping of
    multiple user names in a single line, which is particularly useful for
    simple syntax substitutions.  For example, these entries