Move everything bytes-related into its own module, and re-export
both bytes and primitive in a flat space from wire/mod.rs.
Expose this if a `wire` feature flag is set. We only have `async` stuff
in here.
Change-Id: Ia4ce4791f13a5759901cc9d6ce6bd6bbcca587c7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11389
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: Brian Olsen <me@griff.name>
Put behind the "cloud" backend, like in the `tvix-castore` crate.
Change-Id: Ib38d198baf11ab2a4b6dc405121676147c424611
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11362
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
This adds a Directory service using
https://cloud.google.com/bigtable/docs/ as a K/V store.
Directory (closures) are put in individual keys.
We don't do any bucketed upload of directory closures (yet), as castore/
fs does query individually, does not request recursively (and buffers).
This will be addressed by store composition at some point.
Change-Id: I7fada45bf386a78b7ec93be38c5f03879a2a6e22
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11212
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>
This deals with writing byte packets of larger sizes to an underlying
AsyncWrite.
Its constructor receives the expected size. It also deals with writing
padding if flush/shutdown is called after writing all the payload.
Change-Id: I8acbf992467f3862ffb8c7d669e8c0c8eced14c1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11355
Reviewed-by: picnoir picnoir <picnoir@alternativebit.fr>
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Brian Olsen <me@griff.name>
Tested-by: BuildkiteCI
This introduces rstest-based tests. We also add fixtures for creating
some BlobService / DirectoryService out of thin air.
To test a PathInfoService, we don't really care too much about its
internal storage - ensuring they work is up to the castore tests.
Change-Id: Ia62af076ef9c9fbfcf8b020a781454ad299d972e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11272
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
This creates test scenarios (using the DirectoryService trait) that we
want all DirectoryService implementations to pass.
Some of these tests are ported from proto::tests::grpc_directoryservice,
which tested this on the gRPC interface (rather than the trait),
some others ensure certain behaviour for which we only recently
introduced general checking logic (through ClosureValidator).
We also borrow some code related to setting up a gRPC DirectoryService
client (connecting to a server exposing a in-memory DiretoryService)
from castore::utils, this will be deleted once it's all ported over.
Change-Id: I6810215a76101f908e2aaecafa803c70d85bc552
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11247
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
We had max_level_debug, not max_level_trace, so it was not possible to
have `RUST_LOG` emit trace-level values (at least for our crates).
release_max_level_info still controls the level for release builds, so
that's not affected.
Change-Id: I1f127ab63f13b1622d6616e06759a9414d9bb201
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11208
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
This controls whether tvix-castore has support for various cloud
backends or not.
Use this to control the set of feature flags for the object_store
backend, and only enable the aws, azure and gcp ones if it's set.
In the future this can be used to enable/disable other cloud backends
too.
Without feature flags, `object_store` already supports the `InMemory`
and `LocalFilesystem` backends, and we also want to unconditionally
enable the `http` one. Make sure at least the construction of these
services is covered in the tests.
Similarly, the tvix-store crate, which provides the tvix-store CLI has a
`cloud` feature flag too (defaulting to enabled).
Change-Id: I9fb9c87b740e7dc83f8ff7a0862905d036d513f2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11204
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This allows selectively increasing the log level for only parts of the
stack.
For example, the following RUST_LOG env var enables "tracing" level
logging for `tvix_store` and `tvix_castore`, while keeping it at "info"
for the rest of the stack:
export RUST_LOG='info,tvix_store=trace,tvix_castore=trace'
It only affects logs, not traces (if enabled).
Change-Id: Ib936bd132a405f216e75c843db83fbd71d20a18a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11182
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
This bumps tonic and surrounding crates to 0.11.x.
We added support for tonic 0.11.x into tokio-listener
(https://github.com/vi/tokio-listener/pull/4), so that's bumped as well.
Change-Id: Icfade5894403228299836fefb21b2f9ae59dbebb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11156
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
This brings some initial Nix wire format parsing code, used in the nix
daemon protocol, remote store/builder protocol, as well as the NAR
format itself (note we already have more specialized code for the last
one).
Thanks to embr, this code already exists, in
https://codeberg.org/gorgon/gorgon/src/branch/main/nix-daemon/src/wire.rs,
and we can vendor it into here, as EUPL is compatible with GPL (in that
direction).
The code uses the tokio::io Reader and Writer traits, not the ones from
the `futures` crate, as they provide some more convenient `read_u64_le`
functions.
More application-specific parsing code, as well as code to read strings,
or bytes are left out for now, as we want to be be more restrictive
w.r.t allowed max sizes, and need to parse bytes, not strings.
The code slightly diverges, as we have clippy looped into CI.
`Ok(…?)` can be turned into just the inner expression, and
some .and_then can be expressed in a simpler fashion.
Change-Id: Ie3adcb485e9d66786673b1962a08d4e5df3781d9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11148
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: picnoir picnoir <picnoir@alternativebit.fr>
This uses the `object_store` crate to expose a tvix-castore BlobService
backed by object storage.
It's using FastCDC to chunk blobs into smaller chunks when writing to
it.
These are exposed at the .chunks() method.
Change-Id: I2858c403d4d6490cdca73ebef03c26290b2b3c8e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11076
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
Reviewed-by: Brian Olsen <me@griff.name>
Add a new AsyncRead wrapper, DecompressedReader, that wraps an
underlying AsyncRead, but sniffs the magic bytes at the start of the
stream to determine which compression format is being used out of the
three that are supported by builtins.fetchTarball, and switches to the
correct decompression algorithm adapter dynamically.
This will be used in the implementation of builtins.fetchTarball
Change-Id: I892a4683d5c93e67d4c173f3d21199bdc6605922
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11019
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Implement the fetchurl builtin, and lay the groundwork for implementing
the fetchTarball builtin (which works very similarly, and is implemented
using almost the same code in C++ nix).
An overview of how this works:
1. First, we check if the store path that *would* result from the
download already exists in the store - if it does, we just return
that
2. If we need to download the URL, TvixStoreIO has an `http_client:
reqwest::Client` field now which we use to make the request
3. As we're downloading the blob, we hash the data incrementally into a
SHA256 hasher
4. We compare the hash against the expected hash (if any) and bail out
if it doesn't match
5. Finally, we put the blob in the store and return the store path
Since the logic is very similar, this commit also implements a *chunk*
of `fetchTarball` (though the actual implementation will likely include
a refactor to some of the code reuse here).
The main thing that's missing here is caching of downloaded blobs when
fetchurl is called without a hash - I've opened b/381 to track the TODO
there.
Adding the `SSL_CERT_FILE` here is necessary to teach reqwest how to
load it during tests - see 1c16dee20 (feat(tvix/store): use reqwests'
rustls-native-roots feature, 2024-03-03) for more info.
Change-Id: I83c4abbc7c0c3bfe92461917e23d6d3430fbf137
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11017
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: aspen <root@gws.fyi>
Otherwise this causes conflicts when adding a more recent zstd version
to another crate.
Change-Id: I02d1b1a37f18711c0969cb04e761e967fc4655dc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11100
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
This makes reqwest honor `SSL_CERT_FILE` - previously it was using the
chain bundled in webpki-roots.
`object_store` pulls in `reqwest` with this feature, and the cargo
solver will enable that feature globally as soon as we pull it in, as it
assumes features are additive.
This requires setting `SSL_CERT_FILE` when running tests, otherwise
they'll fail with the unhelpful "NotFound" error.
This was quite some fun to debug, why adding `object_store` to
tvix-castore suddenly made tvix-store tests fail!
Change-Id: I64fc82b4d994715480efdb1ffecb279716456ab9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11090
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This allows calling .into() to get a B3Digest.
Change-Id: I6e63b496413cd00d84acfcd15c7de0f64c79721f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11086
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Implements md5, sha1, sha256 and sha512 using the related crates from
the RustCrypto hashes project (https://github.com/RustCrypto/hashes)
Change-Id: I00730dea44ec9ef85309edc27addab0ae88814b8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11005
Tested-by: BuildkiteCI
Reviewed-by: aspen <root@gws.fyi>
We add a new set of builtins called `import_builtins`, which
will contain import-related builtins, such as `builtins.path` and
`builtins.filterSource`. Both can import paths into the store, with
various knobs to alter the result, e.g. filtering, renaming, expected
hashes.
We introduce `filtered_ingest` which will drive the filtered ingestion
via the Nix function via the generator machinery, and then we register
the root node to the path info service inside the store.
`builtins.filterSource` is very simple, `builtins.path` is a more
complicated model requiring the same logic albeit more sophisticated
with name customization, file ingestion method and expected SHA-256.
Change-Id: I1083f37808b35f7b37818c8ffb9543d9682b2de2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10654
Autosubmit: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
That's one possible abstraction to drive builds.
Whenever IO into a store path is requested, we look up the root node,
and in case we don't have it in PathInfoService, but KnownPaths gives us
a Derivation for that output path, trigger a build and await the result.
This recursively might trigger builds for parent paths if they haven't
been built yet.
Another option would be to simply expose a PathInfoService interface for
a builder too, and loop all building into IO via PathInfoService
composition - but let's start with something.
Note tvix-cli doesn't have a configurable BuildService yet, it's plugged
to the DummyBuildService, so whenever it needs to do a build, it'll fail,
but that's how it can be provoked:
```
(builtins.readFile (import <nixpkgs> {}).hello.outPath + "/bin/hello")
[…]
error[E029]: I/O error: /nix/store/cg8a576pz2yfc1wbhxm1zy4x7lrk8pix-hello-2.12.1: builds are not supported with DummyBuildService
--> [code]:1:2
|
1 | (builtins.readFile (import <nixpkgs> {}).hello.outPath + "/bin/hello")
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Note how this fails, while pure output path calculation
(`(import <nixpkgs> {}).hello.outPath + "/bin/hello")`) still succeeds.
Change-Id: Id2075d8a2b18554d0dd608b4b29146a8cd411e7f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10793
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
No otlp yet, this simply gives us structured log output and a cli
argument for the log level.
Change-Id: Ifaa60bae419640e92baebb6ee59eedd775c769c2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10853
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
This is was dropped accidentially, but we actually want to run tests in
debug mode, to check for overflows.
Change-Id: Ic0cf2d4a263bfd71f3453ed335d8be9dacd945e8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10932
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
C++ nix uses C-style zero-terminated char pointers to represent strings
internally - however, up to this point, tvix has used Rust `String` and
`str` for string values. Since those are required to be valid utf-8, we
haven't been able to properly represent all the string values that Nix
supports.
To fix that, this change converts the internal representation of the
NixString struct from `Box<str>` to `BString`, from the `bstr` crate -
this is a wrapper around a `Vec<u8>` with extra functions for treating
that byte vector as a "morally string-like" value, which is basically
exactly what we need.
Since this changes a pretty fundamental assumption about a pretty core
type, there are a *lot* of changes in a lot of places to make this work,
but I've tried to keep the general philosophy and intent of most of the
code in most places intact. Most notably, there's nothing that's been
done to make the derivation stuff in //tvix/glue work with non-utf8
strings everywhere, instead opting to just convert to String/str when
passing things into that - there *might* be something to be done there,
but I don't know what the rules should be and I don't want to figure
them out in this change.
To deal with OS-native paths in a way that also works in WASM for
tvixbolt, this also adds a dependency on the "os_str_bytes" crate.
Fixes: b/189
Fixes: b/337
Change-Id: I5e6eb29c62f47dd91af954f5e12bfc3d186f5526
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10200
Reviewed-by: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Reviewed-by: sterni <sternenseemann@systemli.org>
Autosubmit: aspen <root@gws.fyi>
Tested-by: BuildkiteCI
TvixStoreIO triggers builds whenever IO into a not-yet-built store path
is requested, if it knows how to build that path.
Change-Id: If30e9db6be2f2a30cbc9d0576f357f3ecfa0d35a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10645
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This is an additional test suite on the top of the Nix ones
for context strings matters.
It already smoked out multiple mistakes and potential bugs and non-deterministic result from the evaluator.
It uses a similar technology as the one in the tvix-eval albeit we instantiate a fully fledged evaluator
with in-memory store.
We copy the files instead of symlinking them because crates are built in
isolation, so symlinks cannot work.
Change-Id: I63ae225ce4f83c6e2c8ccd60d779c2f8eb9d08fb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10619
Autosubmit: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Previously, we were assembling very naively an attribute set composed of context we saw.
But it was forgetting that `"${drv}${drv.drvPath}"` would contain 2 contexts with the same key, but
with different values, one with `outputs = [ "out" ];` and `allOutputs = true;`.
Following this reasoning and comparing with what Nix does, we ought to merge underlying values systematically.
Hence, I bring `itertools` to perform a group by on the key and merge everything on the fly, it's not
beautiful but it's the best I could find, notice that I don't use
`group_by` but I talk about group by, that is, because `group_by` is a
`group_by_consecutive`, see
https://github.com/rust-itertools/itertools/issues/374.
Initially, I tried to do it without a `into_grouping_map_by`, it was akin to assemble the final `NixAttrs` directly,
it was less readable and harder to pull out because we don't have a lot of in-place mutable functions on
our data structures.
Change-Id: I9933c9bd88ffe04de50dda14f21879b60d8b8cd4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10620
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
`test-generator` has not been updated in the past 2 years.
`rstest` has not been updated in the past 5 months.
This is an improvement in the maintenance state… I guess?
We get also new features, it changes the name of the tests with numbers too.
Change-Id: I5376104c7704f525dba7524da78daa09867cc669
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10623
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
We need to vendor in the package expression, as it's not possible to
override cargoHash.
Change-Id: Ib123647bb9b96d41f4630daa431d020f1cb8d4fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10624
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
This starts a BuildService as a separate process, currently defaulting
to the DummyBuildService.
Change-Id: Ic206f00831641d3ffebaa44883b7dc053700b9ca
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10631
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This allows constructing a BuildService from a URI, similar to how it's
done in tvix-[ca]store.
Change-Id: Ib962b329535c6c7e378ab7ac7f4dd254366497b3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10630
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
Also provide a dummy implementation that just fails on any build that's
requested.
Change-Id: I0df743a730c5331ec9ce6e97a966abe18ce067f5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10627
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
This adds support to handle the __structuredAttrs argument, which can be
passed to builtins.derivationStrict.
If __structuredAttrs is passed, and set to true, most of the arguments
passed to builtins.derivationStrict are not simply coerced to a string
and passed down to "environments", but instead kept in a more structured
fashion.
Inside ATerm, which is what's relevant as far as path calculation is
concerned, a virtual `__json` environment variable is present,
containing these structured values.
Inside Builds, these structured values are not made available as an
environment variable, but a JSON file (and source-able bash script).
This will need to be respected once we start emitting BuildRequests,
and for that we can probably just parse the `__json` key in
Derivation.environment again - or keep this additionally in
non-serialized form around during Evaluation.
No matter what, this is left for a followup CL.
The existing handle_derivation_parameters and populate_outputs helper
function were removed, as __structuredAttrs causes quite a change
in behaviour, and so handling both in the same place makes it more
readable.
There's some open questions w.r.t. string contexts for structured attrs
itself. A TODO is left for this, but at least path calculation for
individual structured attrs derivations are correct now.
Part of b/366.
Change-Id: Ic293822266ced6f8c4826d8ef0d2e098a4adccaa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10604
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
This extends derivation_to_build_request to handle passAsFile the same
way Nix does, and adds a unit test for it.
I opted to making this function fallible (if passAsFile contains a
non-existent env var), rather than pushing all of this into the
Derivation validate function.
Change-Id: I75b635f1f6c0c78d72b9a8fc7824f77e97b69951
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10522
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
And include a test to ensure we show the warning.
Change-Id: Ib6a436dbba2592b398b54e44f15a48d1aa345099
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10470
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
This is behind the otlp feature flag (currently enabled by default).
By default, this will try to push traces to a OTLP collector running at
https://localhost:4317.
You can make one available by running:
```
docker run -d --name jaeger \
-e COLLECTOR_ZIPKIN_HOST_PORT=:9411 \
-e COLLECTOR_OTLP_ENABLED=true \
-p 6831:6831/udp \
-p 6832:6832/udp \
-p 5778:5778 \
-p 16686:16686 \
-p 4317:4317 \
-p 4318:4318 \
-p 14250:14250 \
-p 14268:14268 \
-p 14269:14269 \
-p 9411:9411 --rm \
jaegertracing/all-in-one:1.42
```
Started like that, jaeger brings a web interface at
http://localhost:16686/search
As documented in
https://docs.rs/opentelemetry-otlp/latest/opentelemetry_otlp/, you can
point this to another location by setting `OTEL_EXPORTER_OTLP_ENDPOINT`.
Change-Id: Id1dca367d70027b2ea98bb70bcf99a68363ec2be
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8194
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: aaqaishtyaq <aaqaishtyaq@gmail.com>
cl/10378 did already move store/fs to castore/fs, but we kept the tests
in tvix-store, as they were populating a PathInfoService to make nodes
appear in the mount root.
Update these tests to now just insert root nodes into a BTreeMap, and
ensure we can use that as a RootNodes too.
Change-Id: Iad7d1ee4f9423eb6e3a1da33f433842c9ae0de1f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10410
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
With the recent introduction of the RootNodes trait, there's nothing in
the fs module pulling in tvix-store dependencies, so it can live in
tvix-castore.
This allows other crates to make use of TvixStoreFS, without having to
pull in tvix-store.
For example, a tvix-build using a fuse mountpoint at /nix/store doesn't
need a PathInfoService to hold the root nodes that should be present,
but just a list.
tvix-store now has a pathinfoservice/fs module, which contains the
necessary glue logic to implement the RootNodes trait for a
PathInfoService.
To satisfy Rust orphan rules for trait implementations, we had to add a
small wrapper struct. It's mostly hidden away by the make_fs helper
function returning a TvixStoreFs.
It can't be entirely private, as its still leaking into the concrete
type of TvixStoreFS.
tvix-store still has `fuse` and `virtiofs` features, but they now simply
enable these features in the `tvix-castore` crate they depend on.
The tests for the fuse functionality stay in tvix-store for now, as
they populate the root nodes through a PathInfoService.
Once above mentioned "list of root nodes" implementation exists, we
might want to shuffle this around one more time.
Fixes b/341.
Change-Id: I989f664827a5a361b23b34368d242d10c157c756
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10378
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
