Add a composefs Rust crate

Right now this includes just a parser/generator for dump files,
which is helpful for e.g. a flow like taking a tarball, parsing
it in Rust, and then serializing the entry to a composefs dumpfile line.

I'd like to add more opinionated and advanced functionality
related to composefs implemented in this crate - *especially* integration
with containers/OCI.  My thought is that in the short term we can
publish this crate without having the core
C code depend on it.

I plan to use this crate in bootc.

However, more medium term, it may make sense to offer a CLI
tool from this crate, in which case there will be some tension with
the CLI tools that happen to be implemented in C, as commonly
people would

Signed-off-by: Colin Walters <[email protected]>

.github/workflows/rust.yml

@@ -0,0 +1,43 @@
+# Inspired by https://github.com/rust-analyzer/rust-analyzer/blob/master/.github/workflows/ci.yaml
+# but tweaked in several ways.  If you make changes here, consider doing so across other
+# repositories in e.g. ostreedev etc.
+name: Rust
+
+permissions:
+  actions: read
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch: {}
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
+    steps:
+      - uses: actions/checkout@v3
+      # xref containers/containers-image-proxy-rs
+      - name: Cache Dependencies
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: "tests"
+      - name: cargo fmt (check)
+        run: cargo fmt -- --check -l
+      - name: Build
+        run: cargo test --no-run
+      - name: Run tests
+        run: cargo test -- --nocapture --quiet
+  cargo-deny:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: EmbarkStudios/cargo-deny-action@v1
+      with:
+        log-level: warn
+        command: check bans sources licenses

.gitignore

@@ -26,3 +26,5 @@ composefs.spec
 libtool
 ltmain.sh
 missing
+target/
+Cargo.lock

Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "composefs"
+version = "0.1.0"
+edition = "2021"
+description = "Rust composefs"
+keywords = ["composefs", "oci", "opencontainers", "docker", "podman"]
+license = "MIT"
+repository = "https://github.com/containers/composefs"
+rust-version = "1.70.0"
+
+include = [
+    "/COPYING",
+    "/README.md",
+    "/rust/**",
+]
+
+[lib]
+name = "composefs"
+path = "rust/src/lib.rs"
+
+[dependencies]
+anyhow = "1.0"
+libc = "0.2"
+
+[dev-dependencies]
+tar = "0.4.38"
+tempfile = "3.2.0"

deny.toml

@@ -0,0 +1,10 @@
+[licenses]
+unlicensed = "deny"
+allow = ["Apache-2.0", "Apache-2.0 WITH LLVM-exception", "MIT", "BSD-3-Clause", "BSD-2-Clause", "Unicode-DFS-2016"]
+
+[bans]
+
+[sources]
+unknown-registry = "deny"
+unknown-git = "deny"
+allow-git = []