change handling of standard input

For `-f /dev/stdin`, the `pathname` of the parsing context will be empty
as for any other streamed input.

`instance_t::include_directive` did not work as expected for `-f /dev/stdin`
and relative file names. One would expect them to be relative to the current
directory rather than `/dev`.

This will lead to `While parsing file ""` messages. This could be
adjusted to read `While parsing standard input`, but maybe it's not
worth the special cases.

This commit also fixes bug 788: behaviour of source_context for '-f -'

1 files changed, 1 insertions, 1 deletions

diff --git a/src/error.cc b/src/error.cc
index 58339db7..8aa1d3d6 100644
--- a/src/error.cc
+++ b/src/error.cc
@@ -84,7 +84,7 @@ string source_context(const path&            file,
                       const string&          prefix)
 {
   const std::streamoff len = end_pos - pos;
-  if (! len || file == path("/dev/stdin"))
+  if (! len || file.empty())
     return _("<no source context>");
 
   assert(len > 0);