When the HTML output dir is specified using --dir=~/foo, the tilde
needs to be expanded by mkhowto, since the shell won't touch it except
at the start of the complete argument.
diff --git a/Doc/tools/mkhowto b/Doc/tools/mkhowto
index 4fe97fb..d0ab63c 100755
--- a/Doc/tools/mkhowto
+++ b/Doc/tools/mkhowto
@@ -205,7 +205,7 @@
             elif opt == "--dir":
                 if os.sep == "\\":
                     arg = re.sub("/", "\\", arg)
-                self.builddir = arg
+                self.builddir = os.path.expanduser(arg)
             elif opt == "--paper":
                 self.paper = arg
             elif opt == "--dvips-safe":