Fix preprocessor use and config file precedence in piesctl

* NEWS: Document changes.
* doc/pies.texi: Document changes.
* src/cmdline.opt: Don't set preprocessor if DEFAULT_PREPROCESSOR
is NULL.
* src/piesctl-cl.opt: New options: --preprocessor,
--no-preprocessor.
* src/piesctl.c (parse_config): If either client.url or
default_url is set in the program-specific config, use it
and don't parse pies.conf.  This is consistent with the
documented behavior.
(main): Initialize grecs_preprocessor.

1 files changed, 10 insertions, 2 deletions

diff --git a/doc/pies.texi b/doc/pies.texi
index d5b39ca..747c7ea 100644
--- a/doc/pies.texi
+++ b/doc/pies.texi
@@ -3357,13 +3357,21 @@ for a description of allowed URL forms.
 Enable verbose diagnostics.
 @end table
 
-Before parsing, configuration file is preprocessed using
-@command{m4}.  The following options control this feature:
+Before parsing, configuration file is preprocessed using external
+command defined at buid time (normally @command{m4}).  The following
+options control this feature:
 
 @table @option
 @item -E
 Show preprocessed configuration on stdout and exit.
 
+@item --no-preprocessor
+Disable the use of the external preprocessor.
+
+@item --preprocessor=@var{cmd}
+Use the command @var{cmd} as the external preprocessor, instead of the
+default @command{m4}.
+
 @item --define=@var{sym}[=@var{value}]
 @itemx -D @var{symbol}[=@var{value}]
 Define symbol @var{sym} as having @var{value}, or empty, if