Allow $ver placeholder in URL names (#125)

Just like the $ver placeholder is supported for the URL itself.

Signed-off-by: Tom Wieczorek <tom@bibbu.net>

README.md

@@ -194,6 +194,7 @@ How do we fetch the package source if we have the target version number?
 - `fetch.docker = owner/name`
 
 Optional config for `nix-prefetch-url`, applies when the fetcher equals to `fetch.url`.
+`$ver` is available in string, just like for the fetch config.
 
 - `url.name = file_name`
 

app/Config/PackageFetcher.hs

@@ -121,7 +121,7 @@ urlDecoder :: Decoder PackageFetcher
 urlDecoder = do
   url <- getFields ["fetch", "url"]
   name <- getFieldsOpt ["url", "name"]
-  pure $ \(coerce -> v) -> urlFetcher' (T.replace "$ver" v url) name
+  pure $ \(coerce -> v) -> urlFetcher' (T.replace "$ver" v url) (fmap (T.replace "$ver" v) name)
 
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