swarm/api: support mounting manifests via FUSE (#3690)

vendor/bazil.org/fuse/error_std.go

@@ -0,0 +1,31 @@
+package fuse
+
+// There is very little commonality in extended attribute errors
+// across platforms.
+//
+// getxattr return value for "extended attribute does not exist" is
+// ENOATTR on OS X, and ENODATA on Linux and apparently at least
+// NetBSD. There may be a #define ENOATTR on Linux too, but the value
+// is ENODATA in the actual syscalls. FreeBSD and OpenBSD have no
+// ENODATA, only ENOATTR. ENOATTR is not in any of the standards,
+// ENODATA exists but is only used for STREAMs.
+//
+// Each platform will define it a errNoXattr constant, and this file
+// will enforce that it implements the right interfaces and hide the
+// implementation.
+//
+// https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man2/getxattr.2.html
+// http://mail-index.netbsd.org/tech-kern/2012/04/30/msg013090.html
+// http://mail-index.netbsd.org/tech-kern/2012/04/30/msg013097.html
+// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
+// http://www.freebsd.org/cgi/man.cgi?query=extattr_get_file&sektion=2
+// http://nixdoc.net/man-pages/openbsd/man2/extattr_get_file.2.html
+
+// ErrNoXattr is a platform-independent error value meaning the
+// extended attribute was not found. It can be used to respond to
+// GetxattrRequest and such.
+const ErrNoXattr = errNoXattr
+
+var _ error = ErrNoXattr
+var _ Errno = ErrNoXattr
+var _ ErrorNumber = ErrNoXattr