Add model and serd-sort utility

With all the new functionality, the complexity of the serd-pipe command-line
interface is starting to push the limits of available flags. So, instead of
grafting on further options to control a model, this commit adds a new tool,
serd-sort, which acts somewhat like a stripped-down serd-pipe that stores
statements in a model in memory.

This keeps the complexity (including the user-facing complexity) of any one
tool down, since other more focused tools can be used for streaming tasks in a
pipeline.

In other words, abandon Swissarmyknifeism, take a page from the Unix
philosophy, and try to expose the model functionality to the command-line in a
dedicated focused tool.  The model implementation is tested by using this tool
to run a subset of the usual test suites, and a special suite to test statement
sorting.

1 files changed, 2 insertions, 0 deletions

diff --git a/include/serd/status.h b/include/serd/status.h
index 5aedd5a6..90c8d83c 100644
--- a/include/serd/status.h
+++ b/include/serd/status.h
@@ -40,6 +40,8 @@ typedef enum {
   SERD_BAD_DATA,    ///< Invalid data
   SERD_BAD_LITERAL, ///< Invalid literal
   SERD_BAD_PATTERN, ///< Invalid statement pattern
+  SERD_BAD_CURSOR,  ///< Use of invalidated cursor
+  SERD_BAD_INDEX,   ///< No suitable model index available
 } SerdStatus;
 
 /// Return a string describing a status code