[9front] walk: properly format permissions

[Stephen Gregoratto <dev@sgregoratto.me>]

This patch adds dirmodefmt from fcall.h to pretty-print file
permissions, similarly to ls -l. I didn't notice any performance
degradation.

I hope no-one relied on the old behaviour.

diff -r 4dfbef4fa4ac sys/man/1/walk
--- a/sys/man/1/walk	Sat Apr 03 19:32:47 2021 +0200
+++ b/sys/man/1/walk	Sun Apr 04 10:25:44 2021 +1000
@@ -123,8 +123,6 @@
 .IR ls (1),
 .IR du (1)
 .SH BUGS
-Statfmt character `x' displays permissions as an integer.
-.PP
 Manipulating ifs is a nuisance.
 .PP
 File names are assumed to not contain newlines.
diff -r 4dfbef4fa4ac sys/src/cmd/walk.c
--- a/sys/src/cmd/walk.c	Sat Apr 03 19:32:47 2021 +0200
+++ b/sys/src/cmd/walk.c	Sun Apr 04 10:25:44 2021 +1000
@@ -2,6 +2,7 @@
 #include <libc.h>
 #include <bio.h>
 #include <String.h>
+#include <fcall.h>
 
 int Cflag = 0;
 int uflag = 0;
@@ -70,7 +71,7 @@
 			break;
 		case 'q': Bprint(bout, "%ullx.%uld.%.2uhhx", f->qid.path, f->qid.vers, f->qid.type); break;
 		case 's': Bprint(bout, "%lld", f->length); break;
-		case 'x': Bprint(bout, "%ulo", f->mode); break;
+		case 'x': Bprint(bout, "%M", f->mode); break;
 
 		/* These two  are slightly different, as they tell us about the fileserver instead of the file */
 		case 'D': Bprint(bout, "%ud", f->dev); break;
@@ -250,6 +251,8 @@
 		usage();
 	}ARGEND;
 
+	fmtinstall('M', dirmodefmt);
+
 	if((bout = Bfdopen(1, OWRITE)) == nil)
 		sysfatal("Bfdopen: %r");
 	Blethal(bout, nil);
-- 
Stephen Gregoratto