This provides a pluggable mechanism for defining new fetchers. It adds
a builtin function 'fetchTree' that generalizes existing fetchers like
'fetchGit', 'fetchMercurial' and 'fetchTarball'. 'fetchTree' takes a
set of attributes, e.g.
fetchTree {
type = "git";
url = "https://example.org/repo.git";
ref = "some-branch";
rev = "abcdef...";
}
The existing fetchers are just wrappers around this. Note that the
input attributes to fetchTree are the same as flake input
specifications and flake lock file entries.
All fetchers share a common cache stored in
~/.cache/nix/fetcher-cache-v1.sqlite. This replaces the ad hoc caching
mechanisms in fetchGit and download.cc (e.g. ~/.cache/nix/{tarballs,git-revs*}).
This also adds support for Git worktrees (c169ea5904).
When encountering an unsupported protocol, there's no need to retry.
Chances are, it won't suddenly be supported between retry attempts;
error instead. Otherwise, you see something like the following:
$ nix-env -i -f git://git@github.com/foo/bar
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 335 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 604 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 1340 ms
warning: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1); retrying in 2685 ms
With this change, you now see:
$ nix-env -i -f git://git@github.com/foo/bar
error: unable to download 'git://git@github.com/foo/bar': Unsupported protocol (1)
Sadly 10.15 changed /bin/sh to a shim which executes bash, this means it
can't be used anymore without also opening up the sandbox to allow bash.
Failed to exec /bin/bash as variant for /bin/sh (1: Operation not permitted).
This is used to determine the dependency tree of impure libraries so nix
knows what paths to open in the sandbox. With the less restrictive
defaults it isn't needed anymore.
See documentattion in header and comments in implementation for details.
This is actually done in preparation for floating ca derivations, not
multi-output fixed ca derivations, but the distinction doesn't yet
mattter.
Thanks @cole-h for finding and fixing a bunch of typos.
