Some effort to minimize flake dependencies

For example, if the top-level flake depends on
"nixpkgs/release-19.03", and one of its dependencies depends on
"nixpkgs", then the latter will be mapped to "nixpkgs/release-19.03",
rather than whatever the default branch of "nixpkgs" is. Thus you get
only one "nixpkgs" dependency rather than two.

This currently only works in a breadth-first way, so the other way
around (i.e. if the top-level flake depends on "nixpkgs", and a
dependency depends on "nixpkgs/release-19.03") still results in two
"nixpkgs" dependencies.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/libexpr/flake/flakeref.hh b/src/libexpr/flake/flakeref.hh
index 6b47330a7..39e019dbd 100644
--- a/src/libexpr/flake/flakeref.hh
+++ b/src/libexpr/flake/flakeref.hh
@@ -182,6 +182,12 @@ struct FlakeRef
         return std::get_if<FlakeRef::IsPath>(&data)
             && rev == Hash(rev->type);
     }
+
+    /* Return true if 'other' is not less specific than 'this'. For
+       example, 'nixpkgs' contains 'nixpkgs/release-19.03', and both
+       'nixpkgs' and 'nixpkgs/release-19.03' contain
+       'nixpkgs/release-19.03/<hash>'. */
+    bool contains(const FlakeRef & other) const;
 };
 
 std::ostream & operator << (std::ostream & str, const FlakeRef & flakeRef);