patch 8.1.0728: cannot avoid breaking after a single space.

Problem:    Cannot avoid breaking after a single space.
Solution:   Add the 'p' flag to 'formatoptions'. (Tom Ryder)

runtime/doc/change.txt

@@ -1720,6 +1720,17 @@ j	Where it makes sense, remove a comment leader when joining lines.  For
 		         // in the list ~
 	Becomes:
 		int i;   // the index in the list ~
+p	Don't break lines at single spaces that follow periods.  This is
+	intended to complement 'joinspaces' and |cpo-J|, for prose with
+	sentences separated by two spaces.  For example, with 'textwidth' set
+	to 28: >
+		Surely you're joking, Mr. Feynman!
+<	Becomes: >
+		Surely you're joking,
+		Mr. Feynman!
+<	Instead of: >
+		Surely you're joking, Mr.
+		Feynman!
 
 
 With 't' and 'c' you can specify when Vim performs auto-wrapping:

src/edit.c

@@ -6498,6 +6498,7 @@ internal_format(
 	char_u	*saved_text = NULL;
 	colnr_T	col;
 	colnr_T	end_col;
+	int	wcc;			// counter for whitespace chars
 
 	virtcol = get_nolist_virtcol()
 		+ char2cells(c != NUL ? c : gchar_cursor());
@@ -6559,14 +6560,26 @@ internal_format(
 		/* remember position of blank just before text */
 		end_col = curwin->w_cursor.col;
 
-		/* find start of sequence of blanks */
+		// find start of sequence of blanks
+		wcc = 0;
 		while (curwin->w_cursor.col > 0 && WHITECHAR(cc))
 		{
 		    dec_cursor();
 		    cc = gchar_cursor();
+
+		    // Increment count of how many whitespace chars in this
+		    // group; we only need to know if it's more than one.
+		    if (wcc < 2)
+		        wcc++;
 		}
 		if (curwin->w_cursor.col == 0 && WHITECHAR(cc))
 		    break;		/* only spaces in front of text */
+
+		// Don't break after a period when 'formatoptions' has 'p' and
+		// there are less than two spaces.
+		if (has_format_option(FO_PERIOD_ABBR) && cc == '.' && wcc < 2)
+		    continue;
+
 #ifdef FEAT_COMMENTS
 		/* Don't break until after the comment leader */
 		if (curwin->w_cursor.col < leader_len)

src/option.h

@@ -101,10 +101,11 @@
 #define FO_WHITE_PAR	'w'	/* trailing white space continues paragr. */
 #define FO_AUTO		'a'	/* automatic formatting */
 #define FO_REMOVE_COMS	'j'	/* remove comment leaders when joining lines */
+#define FO_PERIOD_ABBR	'p'	/* don't break a single space after a period */
 
 #define DFLT_FO_VI	"vt"
 #define DFLT_FO_VIM	"tcq"
-#define FO_ALL		"tcroq2vlb1mMBn,awj"	/* for do_set() */
+#define FO_ALL		"tcroq2vlb1mMBn,awjp"	/* for do_set() */
 
 /* characters for the p_cpo option: */
 #define CPO_ALTREAD	'a'	/* ":read" sets alternate file name */

src/testdir/test_textformat.vim

@@ -163,6 +163,32 @@ func Test_text_format()
 	      \ '# 1 xxxxx',
 	      \ '#   foobar'], getline(1, 2))
 
+  " Test the 'p' flag for 'formatoptions'
+  " First test without the flag: that it will break "Mr. Feynman" at the space
+  normal ggdG
+  setl tw=28 fo=tcq
+  call setline('.', 'Surely you''re joking, Mr. Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking, Mr.',
+              \ 'Feynman!'], getline(1, 2))
+  " Now test with the flag: that it will push the name with the title onto the
+  " next line
+  normal ggdG
+  setl fo+=p
+  call setline('.', 'Surely you''re joking, Mr. Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking,',
+              \ 'Mr. Feynman!'], getline(1, 2))
+  " Ensure that it will still break if two spaces are entered
+  normal ggdG
+  call setline('.', 'Surely you''re joking, Mr.  Feynman!')
+  normal gqq
+  call assert_equal([
+              \ 'Surely you''re joking, Mr.',
+              \ 'Feynman!'], getline(1, 2))
+
   setl ai& tw& fo& si& comments&
   enew!
 endfunc

src/version.c

@@ -795,6 +795,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    728,
 /**/
     727,
 /**/