Implement a new function "set-newline-at-eof-mode" which controls how…

… mg handles a missing newline at the end of a file during save. It has 3 possible values: prompt, always and never. prompt is the default, current behavior. always will always add a newline if it is missing. never will never add a newline.

def.h

@@ -329,6 +329,13 @@ struct varentry {
 };
 SLIST_HEAD(vhead, varentry);
 
+/*
+ * Newline at EOF modes.
+ */
+#define	NL_EOF_PROMPT 0
+#define NL_EOF_ALWAYS 1
+#define NL_EOF_NEVER 2
+
 /*
  * Previously from ttydef.h
  */
@@ -689,6 +696,7 @@ int		 notabmode(int, int);
 #endif	/* NOTAB */
 int		 overwrite_mode(int, int);
 int		 set_default_mode(int,int);
+int		 set_newline_at_eof_mode(int,int);
 
 #ifdef REGEX
 /* re_search.c X */
@@ -786,6 +794,7 @@ extern int		 tceeol;
 extern int		 tcinsl;
 extern int		 tcdell;
 extern int		 rptcount;	/* successive invocation count */
+extern int		 nlateofmode;
 
 /* https://github.com/hboetes/mg/issues/7#issuecomment-475869095 */
 #if defined(__APPLE__) || defined(__NetBSD__)

file.c

@@ -690,7 +690,15 @@ writeout(FILE ** ffp, struct buffer *bp, char *fn)
 	lpend = bp->b_headp;
 	eobnl = 0;
 	if (llength(lback(lpend)) != 0) {
-		eobnl = eyorn("No newline at end of file, add one");
+		if (nlateofmode == NL_EOF_PROMPT) {
+			eobnl = eyorn("No newline at end of file, add one");
+		}
+		else if (nlateofmode == NL_EOF_ALWAYS) {
+			eobnl = TRUE;
+		}
+		else if (nlateofmode == NL_EOF_NEVER) {
+			eobnl = FALSE;
+		}
 		if (eobnl != TRUE && eobnl != FALSE)
 			return (eobnl); /* abort */
 	}

funmap.c

@@ -204,6 +204,7 @@ static struct funmap functnames[] = {
 #endif /* REGEX */
 	{setcasereplace, "set-case-replace", 0},
 	{set_default_mode, "set-default-mode", 1},
+	{set_newline_at_eof_mode, "set-newline-at-eof-mode", 1},
 	{setfillcol, "set-fill-column", 1},
 	{setmark, "set-mark-command", 0},
 	{setprefix, "set-prefix-string", 1},

modes.c

@@ -22,6 +22,8 @@ int	 defb_nmodes = 0;
 struct maps_s	*defb_modes[PBMODES] = { &fundamental_mode };
 int	 defb_flag = 0;
 
+int  nlateofmode = NL_EOF_PROMPT;
+
 int
 changemode(int f, int n, char *newmode)
 {
@@ -172,3 +174,34 @@ set_default_mode(int f, int n)
 #endif	/* NOTAB */
 	return (TRUE);
 }
+
+// Assumes buf has size at least 8
+//
+// Check if the input is "prompt", "always", or "never".
+// defaults to prompt.
+int
+name_newline_at_eof_mode(char *buf)
+{
+	if (!strncmp("always", buf, 8))
+		return NL_EOF_ALWAYS;
+	else if (!strncmp("never", buf, 8))
+		return NL_EOF_NEVER;
+	else
+		return NL_EOF_PROMPT;
+}
+
+int
+set_newline_at_eof_mode(int f, int n)
+{
+	char	 modebuf[32], *bufp;
+
+	if ((bufp = eread("Set Newline At EOF Mode: ", modebuf, sizeof(modebuf),
+	    EFNEW)) == NULL)
+		return (ABORT);
+	else if (bufp[0] == '\0')
+		return (FALSE);
+
+	nlateofmode = name_newline_at_eof_mode(modebuf);
+
+	return (TRUE);
+}