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-
-## `invalidateFetcherByDrvHash` {#sec-pkgs-invalidateFetcherByDrvHash}
-
-Use the derivation hash to invalidate the output via name, for testing.
-
-Type: `(a@{ name, ... } -> Derivation) -> a -> Derivation`
-
-Normally, fixed output derivations can and should be cached by their output
-hash only, but for testing we want to re-fetch everytime the fetcher changes.
-
-Changes to the fetcher become apparent in the drvPath, which is a hash of
-how to fetch, rather than a fixed store path.
-By inserting this hash into the name, we can make sure to re-run the fetcher
-every time the fetcher changes.
-
-This relies on the assumption that Nix isn't clever enough to reuse its
-database of local store contents to optimize fetching.
-
-You might notice that the "salted" name derives from the normal invocation,
-not the final derivation. `invalidateFetcherByDrvHash` has to invoke the fetcher
-function twice: once to get a derivation hash, and again to produce the final
-fixed output derivation.
-
-Example:
-
-    tests.fetchgit = invalidateFetcherByDrvHash fetchgit {
-      name = "nix-source";
-      url = "https://github.com/NixOS/nix";
-      rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
-      sha256 = "sha256-7DszvbCNTjpzGRmpIVAWXk20P0/XTrWZ79KSOGLrUWY=";
-    };