refactor: split ecr into library and cli crates

The root package becomes a virtual workspace: `crates/ecr` holds the
library (package name `ecr`) and `crates/ecr-cli` the command line
front-end, which keeps installing the `ecr` binary. No behavior change.

The library must not depend on CLI types, so mount::setup_mounts now
takes the `no_bind` flag instead of a `&Args`.

Cargo.lock

@@ -302,7 +302,6 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "base64",
- "clap",
  "cpio",
  "dirs",
  "flate2",
@@ -323,6 +322,17 @@ dependencies = [
  "zstd",
 ]
 
+[[package]]
+name = "ecr-cli"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "clap",
+ "dirs",
+ "ecr",
+ "tempfile",
+]
+
 [[package]]
 name = "either"
 version = "1.16.0"

Cargo.toml

@@ -1,50 +1,14 @@
-[package]
-name = "ecr"
+[workspace]
+resolver = "2"
+members = ["crates/ecr", "crates/ecr-cli"]
+
+[workspace.package]
 version = "0.1.0"
 edition = "2021"
 rust-version = "1.77"
-description = "Enter chroot environments with Linux namespaces"
 license = "MIT"
 authors = ["Valentin Haudiquet"]
 
-[dependencies]
-# CLI parsing
-clap = { version = "4", features = ["derive", "env"] }
-
-# Config parsing
-serde = { version = "1", features = ["derive"] }
-serde_yaml = "0.9"
-
-# HTTP downloads
-reqwest = { version = "0.13", features = ["blocking", "stream"] }
-
-# Tarball extraction
-tar = "0.4"
-flate2 = "1"
-xz2 = "0.1"
-zstd = "0.13"
-
-# Unix syscall bindings
-nix = { version = "0.31", features = ["fs", "mount", "sched", "signal", "user", "process", "hostname"] }
-
-# Temp directories
-tempfile = "3"
-
-# Error handling
-anyhow = "1"
-
-# Utilities
-dirs = "6"
-which = "7"
-cpio = "0.4"
-base64 = "0.22"
-tokio = { version = "1", features = ["rt-multi-thread", "macros", "io-util"] }
-futures-util = "0.3"
-indicatif = "0.18"
-serde_json = "1"
-libc = "0.2"
-users = "0.11"
-
 [profile.release]
 strip = true
 opt-level = "z"

crates/ecr-cli/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "ecr-cli"
+description = "Enter chroot environments with Linux namespaces"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+authors.workspace = true
+
+# The installed binary keeps the `ecr` name even though the CLI package is
+# `ecr-cli`; the library package owns the `ecr` name for consumers.
+[[bin]]
+name = "ecr"
+path = "src/main.rs"
+
+[dependencies]
+ecr = { path = "../ecr" }
+
+# CLI parsing
+clap = { version = "4", features = ["derive", "env"] }
+
+# Error handling
+anyhow = "1"
+
+# Interim: used by the CLI's inline cache/extraction orchestration until it
+# moves behind the library's rootfs API
+dirs = "6"
+tempfile = "3"

crates/ecr-cli/src/main.rs

@@ -1,37 +1,17 @@
-mod chroot;
 mod cli;
-mod config;
-mod distro;
-mod download;
-mod extract;
-mod kernel;
-mod mount;
-mod namespace;
-mod qemu;
-mod qemu_vm;
-mod utils;
-mod verbose;
-
-/// Print to stderr only when --verbose / -v is active.
-#[macro_export]
-macro_rules! veprintln {
-    ($($arg:tt)*) => {
-        if $crate::verbose::is_verbose() {
-            eprintln!($($arg)*);
-        }
-    };
-}
 
 use anyhow::{Context, Result};
 use clap::Parser;
 
 use cli::Args;
-use config::Config;
-use distro::{
+use ecr::chroot;
+use ecr::config::Config;
+use ecr::distro::{
     map_arch, parse_image_ref, resolve_distro_url, resolve_distro_version, Distro, ImageSource,
 };
-use download::{digest_sidecar, download_image, fetch_oci_digest};
-use extract::extract_tarball;
+use ecr::download::{digest_sidecar, download_image, fetch_oci_digest};
+use ecr::extract::extract_tarball;
+use ecr::{kernel, mount, namespace, qemu, qemu_vm, utils, veprintln, verbose};
 
 fn main() -> Result<()> {
     let args = Args::parse();
@@ -227,7 +207,7 @@ fn namespace_mode(args: Args, rootfs: std::path::PathBuf, config: Config) -> Res
             &rootfs_clone,
             &bind_paths_clone,
             &bind_rw_paths_clone,
-            &args_clone,
+            args_clone.no_bind,
         )?;
 
         // Write resolv.conf with DNS from config

crates/ecr/Cargo.toml

@@ -0,0 +1,43 @@
+[package]
+name = "ecr"
+description = "Ephemeral chroot environments with Linux namespaces"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[dependencies]
+# Config parsing
+serde = { version = "1", features = ["derive"] }
+serde_yaml = "0.9"
+
+# HTTP downloads
+reqwest = { version = "0.13", features = ["blocking", "stream"] }
+
+# Tarball extraction
+tar = "0.4"
+flate2 = "1"
+xz2 = "0.1"
+zstd = "0.13"
+
+# Unix syscall bindings
+nix = { version = "0.31", features = ["fs", "mount", "sched", "signal", "user", "process", "hostname"] }
+
+# Temp directories
+tempfile = "3"
+
+# Error handling
+anyhow = "1"
+
+# Utilities
+dirs = "6"
+which = "7"
+cpio = "0.4"
+base64 = "0.22"
+tokio = { version = "1", features = ["rt-multi-thread", "macros", "io-util"] }
+futures-util = "0.3"
+indicatif = "0.18"
+serde_json = "1"
+libc = "0.2"
+users = "0.11"

crates/ecr/src/lib.rs

@@ -0,0 +1,30 @@
+//! ecr — ephemeral chroot environments with Linux namespaces.
+//!
+//! This crate is the library behind the `ecr` CLI. It resolves distro and
+//! OCI image references, downloads them through a content cache, extracts
+//! the rootfs into a scratch directory, and runs commands inside
+//! unprivileged user/PID/mount/UTS namespaces — or boots it in a QEMU VM
+//! (see the `qemu_vm` module).
+
+pub mod chroot;
+pub mod config;
+pub mod distro;
+pub mod download;
+pub mod extract;
+pub mod kernel;
+pub mod mount;
+pub mod namespace;
+pub mod qemu;
+pub mod qemu_vm;
+pub mod utils;
+pub mod verbose;
+
+/// Print to stderr only when verbose mode is active (see [`verbose::set`]).
+#[macro_export]
+macro_rules! veprintln {
+    ($($arg:tt)*) => {
+        if $crate::verbose::is_verbose() {
+            eprintln!($($arg)*);
+        }
+    };
+}

crates/ecr/src/mount.rs

@@ -21,15 +21,13 @@ fn escape_overlay_path(path: &Path) -> Result<String> {
     Ok(s.replace('\\', "\\\\").replace(',', "\\,"))
 }
 
-use crate::cli::Args;
-
 /// Setup all required mounts inside the chroot
 /// Returns a TempDir that must be kept alive for the duration of the chroot
 pub fn setup_mounts(
     rootfs: &Path,
     bind_paths: &[std::path::PathBuf],
     bind_rw_paths: &[std::path::PathBuf],
-    args: &Args,
+    no_bind: bool,
 ) -> Result<Vec<TempDir>> {
     // Keep all overlay temp dirs alive
     let mut overlay_temps: Vec<TempDir> = Vec::new();
@@ -60,7 +58,7 @@ pub fn setup_mounts(
     }
 
     // Setup overlay mounts for bind paths (read-only via overlay)
-    if !args.no_bind {
+    if !no_bind {
         for bind_path in bind_paths {
             // Skip if this path is also in bind_rw (bind_rw takes precedence)
             if !bind_rw_paths.contains(bind_path) {

crates/ecr/src/utils.rs

@@ -42,6 +42,9 @@ pub enum Arch {
 
 impl Arch {
     /// Get the architecture from a string (any common naming convention)
+    /// Not a FromStr impl: unrecognized names map to Arch::Unknown rather
+    /// than an error, by design.
+    #[allow(clippy::should_implement_trait)]
     pub fn from_str(s: &str) -> Self {
         match s {
             "amd64" | "x86_64" | "x64" => Arch::Amd64,