Call ZIP_SOURCE_SUPPORTS when creating a source, only call supported commands.

lib/zip.h

diff --git a/lib/zip.h b/lib/zip.h
index c2b3032..5539930 100644
--- a/lib/zip.h
+++ b/lib/zip.h
@@ -231,6 +231,29 @@
 };
 typedef enum zip_source_cmd zip_source_cmd_t;
 
+#define ZIP_SOURCE_MAKE_COMMAND_BITMASK(cmd)    (1<<(cmd))
+
+#define ZIP_SOURCE_SUPPORTS_READABLE	(ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_OPEN) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_READ) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_CLOSE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_STAT) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_ERROR) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_FREE))
+
+#define ZIP_SOURCE_SUPPORTS_SEEKABLE	(ZIP_SOURCE_SUPPORTS_READABLE \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_SEEK) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_TELL) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_SUPPORTS))
+
+#define ZIP_SOURCE_SUPPORTS_WRITABLE    (ZIP_SOURCE_SUPPORTS_SEEKABLE \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_BEGIN_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_COMMIT_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_ROLLBACK_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_SEEK_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_TELL_WRITE) \
+                                         | ZIP_SOURCE_MAKE_COMMAND_BITMASK(ZIP_SOURCE_REMOVE))
+
 /* for use by sources */
 struct zip_source_args_seek {
     zip_int64_t offset;