/** Substitute meta-variables in string \p s, making use of \p params and
\p buffer.
If \p external_in_tmpdir is true, all files are assumed to be in the
/** Substitute meta-variables in string \p s, making use of \p params and
\p buffer.
If \p external_in_tmpdir is true, all files are assumed to be in the
place in the buffer's temporary directory.
*/
int writeExternal(InsetExternalParams const &,
std::string const & format,
Buffer const &,
place in the buffer's temporary directory.
*/
int writeExternal(InsetExternalParams const &,
std::string const & format,
Buffer const &,