implement Identifier field for IndexTargets

A frontend like apt-file is only interested in a specific set of files
and selects those easily via "Created-By". If it supports two locations
for those files through it would need to select both and a user would
need to know that implementation detail for sources.list configuration.

The "Identifier" field is hence introduced which by default has the same
value as "Created-By", but can be freely configured – especially it can
be used to give two indexes the same identifier.

1 files changed, 1 insertions, 0 deletions

diff --git a/apt-pkg/indexfile.h b/apt-pkg/indexfile.h
index eaaded87a..76a3d069e 100644
--- a/apt-pkg/indexfile.h
+++ b/apt-pkg/indexfile.h
@@ -92,6 +92,7 @@ class IndexTarget							/*{{{*/
       BY_HASH,
       KEEPCOMPRESSEDAS,
       FALLBACK_OF,
+      IDENTIFIER,
    };
    std::string Option(OptionKeys const Key) const;
    bool OptionBool(OptionKeys const Key) const;