This allows overriding the name component of the resulting Nix store
path, which is necessary if the base name of the URI contains
"illegal" characters.
This is in particular useful for fetchFromGitHub et al., ensuring that
the store path produced by nix-prefetch-url corresponds to what those
functions expect.
This allows nix-prefetch-url to prefetch the output of fetchzip and
its wrappers (like fetchFromGitHub). For example:
$ nix-prefetch-url --unpack https://github.com/NixOS/patchelf/archive/0.8.tar.gz
or from a Nix expression:
$ nix-prefetch-url -A nix-repl.src
In the latter case, --unpack can be omitted because nix-repl.src is a
fetchFromGitHub derivation and thus has "outputHashMode" set to
"recursive".
For example,
$ nix-prefetch-url -A hello.src
will prefetch the file specified by the fetchurl call in the attribute
‘hello.src’ from the Nix expression in the current directory. This
differs from ‘nix-build -A hello.src’ in that it doesn't verify the
hash.
You can also specify a path to the Nix expression:
$ nix-prefetch-url ~/Dev/nixpkgs -A hello.src
List elements (typically used in ‘patches’ attributes) also work:
$ nix-prefetch-url -A portmidi.patches.0
This makes that option even more insecure, by also not checking the SSL host.
But without this parameter, one can still get SSL errors even when
"verify-https-binary-caches" is false, which is unexpected IMO.
It was strange to show "upgrading" when the version was getting lower.
This is left on "upgrading" when the versions are the same,
as I can't see any better wording.
Until now, if one explicitly installed a low-priority version,
nix-env --upgrade would downgrade it by default and even with --leq.
Let's never accept an upgrade with version not matching the upgradeType.
Additionally, let's never decrease the priority of an installed package;
you can use --install to force that.
Also refactor to use variable bestVersion instead of bestName,
as only version was used from it.
Fixes https://github.com/NixOS/nixpkgs/issues/9504.
Note that this means we may have a non-functional /bin/sh in the
chroot while rebuilding Bash or one of its dependencies. Ideally those
packages don't rely on /bin/sh though.
