avoid opening files as '#foo' during creation of archives
(not just during extraction).

Reference: /n/sources/patch/applied/c-no-number-sign
Date: Sun Dec 18 12:10:02 CET 2005

--- /sys/src/cmd/tar.c	Sun Dec 18 12:09:30 2005
+++ /sys/src/cmd/tar.c	Sun Dec 18 12:09:26 2005
@@ -634,10 +634,20 @@
 	ulong blksleft, blksread;
 	Hdr *hbp;
 	Dir *dir;
+	String *name = nil;
+
+	if (shortf[0] == '#') {
+		name = s_new();
+		s_append(name, "./");
+		s_append(name, shortf);
+		shortf = s_to_c(name);
+	}
 
 	fd = open(shortf, OREAD);
 	if (fd < 0) {
 		fprint(2, "%s: can't open %s: %r\n", argv0, file);
+		if (name)
+			s_free(name);
 		return;
 	}
 	dir = dirfstat(fd);
@@ -650,6 +660,8 @@
 		putbackblk(ar);
 		free(dir);
 		close(fd);
+		if (name)
+			s_free(name);
 		return;
 	}
 	putblk(ar);
@@ -679,6 +691,8 @@
 		if (verbose)
 			fprint(2, "%s\n", file);
 	}
+	if (name)
+		s_free(name);
 }
 
 static char *
@@ -783,7 +797,7 @@
 {
 	int len;
 	static char *last;
-	
+
 	/*
 	 * Always print about files.  Only print about directories
 	 * we haven't printed about.  (Assumes archive is ordered
@@ -805,7 +819,7 @@
 	}
 	fprint(2, "%s: can't create %s: %r\n", argv0, s);
 }
-	
+
 static int
 makedir(char *s)
 {
@@ -826,7 +840,7 @@
 {
 	int err;
 	char *p;
-	
+
 	p = s;
 	err = 0;
 	while (!err && (p = strchr(p+1, '/')) != nil) {