Vendor all dependencies (crates) for Cargo

Add logic to resolve each Cargo package by vendoring its dependencies
(crates) into the output directory using Cargo CLI. The important
option here is `--locked` that disabled any changes to Cargo.lock file.

To use vendored sources, `.cargo/config.toml` must contain the following
lines. See [1] for more details. Replace hardcoded directory path with a
placeholder for output directory specified by the users when running
`cachi2 inject-files ...`

```
[source.crates-io]
replace-with = "vendored-sources"

[source.vendored-sources]
directory = "${path-to-vendored-sources}"
```

---
[1]: https://crates.io/crates/cargo-vendor

Signed-off-by: Michal Šoltis <msoltis@redhat.com>

cachi2/core/package_managers/cargo/main.py

@@ -1,5 +1,15 @@
+import logging
+import textwrap
+
+import tomlkit
+from tomlkit.toml_file import TOMLFile
+
 from cachi2.core.models.input import Request
 from cachi2.core.models.output import Component, EnvironmentVariable, ProjectFile, RequestOutput
+from cachi2.core.rooted_path import RootedPath
+from cachi2.core.utils import run_cmd
+
+log = logging.getLogger(__name__)
 
 
 def fetch_cargo_source(request: Request) -> RequestOutput:
@@ -8,4 +18,42 @@ def fetch_cargo_source(request: Request) -> RequestOutput:
     environment_variables: list[EnvironmentVariable] = []
     project_files: list[ProjectFile] = []
 
+    for package in request.cargo_packages:
+        package_dir = request.source_dir.join_within_root(package.path)
+        components.extend(_resolve_cargo_package(package_dir, request.output_dir))
+        # cargo allows to specify configuration per-package
+        # https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure
+        project_files.append(_use_vendored_sources(package_dir))
+
     return RequestOutput.from_obj_list(components, environment_variables, project_files)
+
+
+def _resolve_cargo_package(package_dir: RootedPath, output_dir: RootedPath) -> list[Component]:
+    """Resolve a single cargo package."""
+    vendor_dir = output_dir.join_within_root("deps/cargo")
+    cmd = ["cargo", "vendor", "--locked", str(vendor_dir)]
+    log.info("Vendoring crates at %s", package_dir)
+    run_cmd(cmd=cmd, params={"cwd": package_dir})
+    return []
+
+
+def _use_vendored_sources(package_dir: RootedPath) -> ProjectFile:
+    """Make sure cargo will use the vendored sources when building the project."""
+    cargo_config = package_dir.join_within_root(".cargo/config.toml")
+    cargo_config.path.parent.mkdir(parents=True, exist_ok=True)
+    cargo_config.path.touch(exist_ok=True)
+
+    template = """
+    [source.crates-io]
+    replace-with = "vendored-sources"
+
+    [source.vendored-sources]
+    directory = "${output_dir}/deps/cargo"
+    """
+
+    toml_file = TOMLFile(cargo_config)
+    original_content = toml_file.read()
+    original_content.update(tomlkit.parse(textwrap.dedent(template)))
+    toml_file.write(original_content)
+
+    return ProjectFile(abspath=cargo_config.path, template=template)

tests/unit/package_managers/cargo/test_main.py

@@ -0,0 +1,42 @@
+import tomlkit
+
+from cachi2.core.package_managers.cargo.main import _use_vendored_sources
+from cachi2.core.rooted_path import RootedPath
+
+
+def test_use_vendored_sources_creates_config_file(rooted_tmp_path: RootedPath) -> None:
+    config_path = rooted_tmp_path.join_within_root(".cargo/config.toml")
+    config_path.path.parent.mkdir(parents=True)
+
+    project_file = _use_vendored_sources(rooted_tmp_path)
+
+    assert config_path.path.exists()
+    assert project_file.abspath == config_path.path
+
+    config_content = tomlkit.parse(config_path.path.read_text())
+
+    assert config_content.get("source") == {
+        "crates-io": {"replace-with": "vendored-sources"},
+        "vendored-sources": {"directory": "${output_dir}/deps/cargo"},
+    }
+
+
+def test_use_vendored_sources_preserves_existing_config(rooted_tmp_path: RootedPath) -> None:
+    config_path = rooted_tmp_path.join_within_root(".cargo/config.toml")
+    config_path.path.parent.mkdir(parents=True)
+
+    some_toml = """
+    [build]
+    rustflags = ["-C", "target-cpu=native"]
+    """
+    config_path.path.write_text(some_toml)
+
+    _use_vendored_sources(rooted_tmp_path)
+
+    config_content = tomlkit.parse(config_path.path.read_text())
+
+    assert config_content.get("build") == {"rustflags": ["-C", "target-cpu=native"]}
+    assert config_content.get("source") == {
+        "crates-io": {"replace-with": "vendored-sources"},
+        "vendored-sources": {"directory": "${output_dir}/deps/cargo"},
+    }