Bring the handling of defective prologues even closer to groff,

in particular relaxing the distinction between prologue and body
and further improving messages.
* The last .Dd wins and the last .Os wins, even in the body.
* The last .Dt before the first body macro wins.
* Missing title in .Dt defaults to UNTITLED.  Warn about it.
* Missing section in .Dt does not default to 1.  But warn about it.
* Do not warn multiple times about the same mdoc(7) prologue macro.
* Warn about missing .Os.
* Incomplete .TH defaults to empty strings.  Warn about it.

1 files changed, 7 insertions, 4 deletions

diff --git a/read.c b/read.c
index 07329dbe..4ad08236 100644
--- a/read.c
+++ b/read.c
@@ -93,16 +93,19 @@ static	const char * const	mandocerrs[MANDOCERR_MAX] = {
 	"generic warning",
 
 	/* related to the prologue */
-	"missing .TH macro, using \"unknown 1\"",
+	"missing manual title, using UNTITLED",
+	"missing manual title, using \"\"",
 	"lower case character in document title",
+	"missing manual section, using \"\"",
 	"unknown manual section",
 	"unknown manual volume or arch",
 	"missing date, using today's date",
 	"cannot parse date, using it verbatim",
-	"prologue macros out of order",
+	"missing Os macro, using \"\"",
 	"duplicate prologue macro",
-	"incomplete prologue, terminated by",
-	"skipping prologue macro in body",
+	"late prologue macro",
+	"skipping late title macro",
+	"prologue macros out of order",
 
 	/* related to document structure */
 	".so is fragile, better use ln(1)",