Add 'sentence-end-double-space'.

If you prefer "lighter" punctuation and one space between sentences,
for example:

Mr and Mrs Jones are from the UK. They arrived today.

over more liberal use of full stops and double spaces between
sentences:

Mr. and Mrs. Jones are from the U.K.  They arrived today.

then toggling 'sentence-end-double-space' will make mg's
fill-paragraph function format text using one space instead of two
(the default) between sentences. However, be careful, should you have
a double spaced document and accidentally "format" it to have single
spaces, then you may have a problem. mg won't be able to revert the
formatting for you (unless you have a previous version of the text in
the "undo" history, or are using mg's backup facility and haven't
opened and saved multiple times!).

Comments from schwarze@

1 files changed, 14 insertions, 3 deletions

diff --git a/usr.bin/mg/paragraph.c b/usr.bin/mg/paragraph.c
index 58237c09998..ca902c393fe 100644
--- a/usr.bin/mg/paragraph.c
+++ b/usr.bin/mg/paragraph.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: paragraph.c,v 1.43 2016/04/12 06:20:50 lum Exp $	*/
+/*	$OpenBSD: paragraph.c,v 1.44 2016/04/14 17:05:32 lum Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -208,12 +208,12 @@ fillpara(int f, int n)
 			 * behave the same way if a ')' is preceded by a
 			 * [.?!] and followed by a doublespace.
 			 */
-			if (!eopflag && ((eolflag ||
+			if (dblspace && (!eopflag && ((eolflag ||
 			    curwp->w_doto == llength(curwp->w_dotp) ||
 			    (c = lgetc(curwp->w_dotp, curwp->w_doto)) == ' '
 			    || c == '\t') && (ISEOSP(wbuf[wordlen - 1]) ||
 			    (wbuf[wordlen - 1] == ')' && wordlen >= 2 &&
-			    ISEOSP(wbuf[wordlen - 2]))) &&
+			    ISEOSP(wbuf[wordlen - 2])))) &&
 			    wordlen < MAXWORD - 1))
 				wbuf[wordlen++] = ' ';
 
@@ -482,3 +482,14 @@ setfillcol(int f, int n)
 	}
 	return (TRUE);
 }
+
+int
+sentencespace(int f, int n)
+{
+	if (f & FFARG)
+		dblspace = n > 1;
+	else
+		dblspace = !dblspace;
+
+	return (TRUE);
+}