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).
Using std::filesystem means also having to link with -lstdc++fs on
some platforms and it's hard to discover for what platforms this is
needed. As all the functionality is already implemented as utilities,
use those instead.
Due to fetchGit not checking if rev is an ancestor of ref (there is even
a FIXME comment about it in the code), the cache repo might not have the
ref even though it has the rev. This doesn't matter when submodule =
false, but the submodule = true code blows up because it tries to fetch
the (missing) ref from the cache repo.
Fix this in the simplest way possible: fetch all refs from the local
cache repo when submodules = true.
TODO: Add tests.
The .link file is used as a lock, so I think we should put the
"submodule" attribute in there since turning on submodules creates a new
.link file path.
If you do a fetchTree on a Git repository, whether the result contains
a revCount attribute should not depend on whether that repository
happens to be a shallow clone or not. That would complicate caching a
lot and would be semantically messy. So applying fetchTree/fetchGit to
a shallow repository is now an error unless you pass the attribute
'shallow = true'. If 'shallow = true', we don't return revCount, even
if the repository is not actually shallow.
Note that Nix itself is not doing shallow clones at the moment. But it
could do so as an optimisation if the user specifies 'shallow = true'.
Issue #2988.
This allows all supported fetchers to be used, e.g.
builtins.fetchTree {
type = "github";
owner = "NixOS";
repo = "nix";
rev = "d4df99a3349cf2228a8ee78dea320afef86eb3ba";
}
Most functions now take a StorePath argument rather than a Path (which
is just an alias for std::string). The StorePath constructor ensures
that the path is syntactically correct (i.e. it looks like
<store-dir>/<base32-hash>-<name>). Similarly, functions like
buildPaths() now take a StorePathWithOutputs, rather than abusing Path
by adding a '!<outputs>' suffix.
Note that the StorePath type is implemented in Rust. This involves
some hackery to allow Rust values to be used directly in C++, via a
helper type whose destructor calls the Rust type's drop()
function. The main issue is the dynamic nature of C++ move semantics:
after we have moved a Rust value, we should not call the drop function
on the original value. So when we move a value, we set the original
value to bitwise zero, and the destructor only calls drop() if the
value is not bitwise zero. This should be sufficient for most types.
Also lots of minor cleanups to the C++ API to make it more modern
(e.g. using std::optional and std::string_view in some places).
Also, fetchGit now runs in O(1) memory since we pipe the output of
'git archive' directly into unpackTarball() (rather than first reading
it all into memory).
Add missing docstring on InstallableCommand. Also, some of these were wrapped
when they're right next to a line longer than the unwrapped line, so we can just
unwrap them to save vertical space.
git show seems to print the entire tag message when being called on a tag
instead of a commit. git log instead always prints the correct timestamp
in my tests.
The error nix prints is: `error: stoull`.
In particular, when building a flake lock file, inputs like 'nixpkgs'
are now downloaded only once. Previously, it would fetch
https://api.github.com/repos/<owner>/<repo>/tarball/<ref> and then
later https://api.github.com/repos/<owner>/<repo>/tarball/<rev>, even
though they produce the same result.
Git and GitHub now also share a cache that maps revs to a store path
and other info.
Fixes
$ nix build
fatal: bad revision 'HEAD'
error: program 'git' failed with exit code 128
on a new flake. It is now detected as a dirty tree with revCount = 0.
Instead of a list, inputs are now an attrset like
inputs = {
nixpkgs.uri = github:NixOS/nixpkgs;
};
If 'uri' is omitted, than the flake is a lookup in the flake registry, e.g.
inputs = {
nixpkgs = {};
};
but in that case, you can also just omit the input altogether and
specify it as an argument to the 'outputs' function, as in
outputs = { self, nixpkgs }: ...
This also gets rid of 'nonFlakeInputs', which are now just a special
kind of input that have a 'flake = false' attribute, e.g.
inputs = {
someRepo = {
uri = github:example/repo;
flake = false;
};
};
Julian Stecklina