[Nix-dev] Why does fetchgit not look at the URL to determine the cache location?

[Bjørn Forsman]

On 31 December 2014 at 17:50, Rico Huijbers <rix0rrr at gmail.com> wrote:
> Hi,
>
> When I copy/paste a fetchgit block from another file, and change the URL and rev without changing the hash, I expect the download to fail (and tell me the hash).
>
> However, what actually happens is that fetchgit just looks at the hash, sees that *something* with that hash has already been downloaded, and happily proceeds with the rest of the script using the wrong source files. Now I have to go and do nix-prefetch-git every time.
>
> Shouldn’t fetchgit build the hash from URL and rev, as opposed to the provided hash? Or am I doing it wrong?

AFAIK, it's the nixos hashed mirror that creates this behaviour.
fetchgit itself will re-download if the _basename_ of the URL changes,
but when the hashed mirror has a file with the given hash, it is
downloaded instead.

So it's the hashed mirror that needs to take the basename of URL into account.

Best regards,
Bjørn Forsman