This is one that Russ suggested a while back.  It
changes the save behavior of acme mail so that ^From
will be escaped with a space.  This keeps readers
of the mbox format from getting confused about message
boundaries.

Reference: /n/sources/patch/applied/acme_mail_save
Date: Wed Apr 15 21:08:51 CES 2009
Signed-off-by: blstuart@bellsouth.net

--- /acme/mail/src/dat.h	Wed Apr 15 21:06:38 2009
+++ /acme/mail/src/dat.h	Wed Apr 15 21:06:35 2009
@@ -118,6 +118,7 @@
 
 extern	void		mkreply(Message*, char*, char*, Plumbattr*, char*);
 extern	void		delreply(Message*);
+extern	int		write2(int, int, char*, int, int);
 
 extern	int		mesgadd(Message*, char*, Dir*, char*);
 extern	void		mesgmenu(Window*, Message*);
--- /acme/mail/src/mesg.c	Wed Apr 15 21:07:21 2009
+++ /acme/mail/src/mesg.c	Wed Apr 15 21:07:16 2009
@@ -571,12 +571,10 @@
 	}
 	free(t);
 
-	all = emalloc(n+k+1);
-	memmove(all, unixheader, k);
-	memmove(all+k, raw, n);
-	memmove(all+k+n, "\n", 1);
-	n = k+n+1;
-	free(unixheader);
+	all = emalloc(n+2);
+	memmove(all, raw, n);
+	memmove(all+n, "\n\0", 1);
+	n = n+1;
 	free(raw);
 	ret = 1;
 	s = estrdup(s);
@@ -586,10 +584,12 @@
 	if(ofd < 0){
 		fprint(2, "Mail: can't open %s: %r\n", s);
 		ret = 0;
-	}else if(seek(ofd, 0LL, 2)<0 || write(ofd, all, n)!=n){
+	}else if(seek(ofd, 0LL, 2)<0 || write(ofd, unixheader, k)!=k
+			|| write2(-1, ofd, all, n, 1)<n){
 		fprint(2, "Mail: save failed: can't write %s: %r\n", s);
 		ret = 0;
 	}
+	free(unixheader);
 	free(all);
 	close(ofd);
 	free(s);
--- /acme/mail/src/reply.c	Wed Apr 15 21:07:27 2009
+++ /acme/mail/src/reply.c	Wed Apr 15 21:07:24 2009
@@ -341,21 +341,20 @@
 	return n;
 }
 
-void
+int
 write2(int fd, int ofd, char *buf, int n, int nofrom)
 {
 	char *from, *p;
-	int m;
+	int m = 0;
 
-	write(fd, buf, n);
+	if(fd >= 0)
+		m = write(fd, buf, n);
 
 	if(ofd <= 0)
-		return;
+		return m;
 
-	if(nofrom == 0){
-		write(ofd, buf, n);
-		return;
-	}
+	if(nofrom == 0)
+		return write(ofd, buf, n);
 
 	/* need to escape leading From lines to avoid corrupting 'outgoing' mailbox */
 	for(p=buf; *p; p+=m){
@@ -374,6 +373,7 @@
 		}
 		n -= m;
 	}
+	return p-buf;
 }
 
 void