pkgs.fetchurl supports an executable argument, which is especially nice
when downloading a large executable. This patch adds the same option to
nix-prefetch-url.
I have tested this to work on the simple case of prefetching a little
executable:
1. nix-prefetch-url --executable https://my/little/script
2. Paste the hash into a pkgs.fetchurl-based package, script-pkg.nix
3. Delete the output from the store to avoid any misidentified artifacts
4. Realise the package script-pkg.nix
5. Run the executable
I repeated the above while using --name, as well.
I suspect --executable would have no meaningful effect if combined with
--unpack, but I have not tried it.
It is apparently required for using `toJSONObject()`, which we do inside
the header file (because it's in a template).
This was accidentally working when building Nix itself (presumably because
`config.hh` was always included after `nlohman/json.hpp`) but caused a
(pretty dirty) build failure in the perl bindings package.
Rework the `Store` hierarchy so that there's now one hierarchy for the
store configs and one for the implementations (where each implementation
extends the corresponding config). So a class hierarchy like
```
StoreConfig-------->Store
| |
v v
SubStoreConfig----->SubStore
| |
v v
SubSubStoreConfig-->SubSubStore
```
(with virtual inheritance to prevent DDD).
The advantage of this architecture is that we can now introspect the configuration of a store without having to instantiate the store itself
Add a new `init()` method to the `Store` class that is supposed to
handle all the effectful initialisation needed to set-up the store.
The constructor should remain side-effect free and just initialize the
c++ data structure.
The goal behind that is that we can create “dummy” instances of each
store to query static properties about it (the parameters it accepts for
example)
Directly register the store classes rather than a function to build an
instance of them.
This gives the possibility to introspect static members of the class or
choose different ways of instantiating them.
Add a fallback path in `queryPartialDerivationOutputMap` for daemons
that don't support it.
Also upstreams a couple methods from `SSHStore` to `RemoteStore` as this
is needed to handle the fallback path.
Otherwise the result of the printing can't be parsed back correctly by
Nix (because the unescaped `${` will be parsed as the begining of an
anti-quotation).
Fix#3989
