acme: add -m option and avoid looking in the mirror

src/cmd/acme/acme.c

@@ -28,6 +28,7 @@ Reffont	*reffonts[2];
 int		snarffd = -1;
 int		mainpid;
 int		swapscrollbuttons = FALSE;
+char		*mtpt;
 
 enum{
 	NSnarf = 1000	/* less than 1024, I/O buffer size */
@@ -106,6 +107,11 @@ threadmain(int argc, char *argv[])
 		if(loadfile == nil)
 			goto Usage;
 		break;
+	case 'm':
+		mtpt = ARGF();
+		if(mtpt == nil)
+			goto Usage;
+		break;
 	case 'r':
 		swapscrollbuttons = TRUE;
 		break;
@@ -1056,3 +1062,13 @@ acmegetsnarf(void)
 	free(r);
 	free(s);
 }
+
+int
+ismtpt(char *file)
+{
+	int n;
+
+	/* This is not foolproof, but it will stop a lot of them. */
+	n = strlen(mtpt);
+	return strncmp(file, mtpt, n) == 0 && ((n > 0 && mtpt[n-1] == '/') || file[n] == '/' || file[n] == 0);
+}

src/cmd/acme/dat.h

@@ -542,6 +542,7 @@ int			erroutfd;
 int			messagesize;		/* negotiated in 9P version setup */
 int			globalautoindent;
 int			dodollarsigns;
+char*		mtpt;
 
 enum
 {

src/cmd/acme/fns.h

@@ -102,3 +102,5 @@ int	abbrevenv(Rune**, uint*);
 #define	runemalloc(a)		(Rune*)emalloc((a)*sizeof(Rune))
 #define	runerealloc(a, b)	(Rune*)erealloc((a), (b)*sizeof(Rune))
 #define	runemove(a, b, c)	memmove((a), (b), (c)*sizeof(Rune))
+
+int	ismtpt(char*);

src/cmd/acme/fsys.c

@@ -121,7 +121,7 @@ fsysinit(void)
 	initfcall();
 	if(pipe(p) < 0)
 		error("can't create pipe");
-	if(post9pservice(p[0], "acme") < 0)
+	if(post9pservice(p[0], "acme", mtpt) < 0)
 		error("can't post service");
 	sfd = p[1];
 	fmtinstall('F', fcallfmt);

src/cmd/acme/look.c

@@ -620,7 +620,7 @@ expandfile(Text *t, uint q0, uint q1, Expand *e)
 	if(w != nil)
 		goto Isfile;
 	/* if it's the name of a file, it's a file */
-	if(access(e->bname, 0) < 0){
+	if(ismtpt(e->bname) || access(e->bname, 0) < 0){
 		free(e->bname);
 		e->bname = nil;
 		goto Isntfile;

src/cmd/acme/text.c

@@ -200,6 +200,10 @@ textload(Text *t, uint q0, char *file, int setqid)
 		warning(nil, "empty directory name");
 		return 0;
 	}
+	if(ismtpt(file)){
+		warning(nil, "will not open self mount point %s\n", file);
+		return 0;
+	}
 	fd = open(file, OREAD);
 	if(fd < 0){
 		warning(nil, "can't open %s: %r\n", file);