fix(cli): mount the config from an absolute --config path correctly

`cb init` built the config bind-mount source as `./{config_path}`. The prefix
is needed for a relative path, which compose would otherwise read as a named
volume, but an absolute path became `.//abs/path`: compose resolves that
against the project directory, docker creates a root-owned directory there,
and the sidecar starts with a DIRECTORY mounted at /cb-config.toml, dying
with `Unable to find config file: "/cb-config.toml": Is a directory`.

The prefix is now added only when the path needs it. Every other mount in the
generated file already passed its path through unchanged.

The init integration test already ran with an absolute --config but asserted
only the mount's container side, so the bug rendered under it; it now pins the
host side too.

Author: JasonVranek

bin/tests/binary.rs

@@ -130,11 +130,16 @@ fn test_init_compose_file_pbs_service_structure() {
     assert_eq!(pbs["image"].as_str(), Some("ghcr.io/commit-boost/commit-boost:latest"), "image");
     assert_eq!(pbs["container_name"].as_str(), Some("cb_pbs"), "container_name");
 
-    // Config file must be mounted inside the container.
+    // Config file must be mounted inside the container, from the path it was
+    // read from. `--config` here is ABSOLUTE, so the source must be that path
+    // verbatim: a `./` prefix would make compose resolve it against the project
+    // directory and docker would create a directory there instead.
     let volumes = pbs["volumes"].as_sequence().expect("volumes is a list");
+    let expected_mount = format!("{}:/cb-config.toml:ro", config.display());
     assert!(
-        volumes.iter().any(|v| v.as_str().map_or(false, |s| s.ends_with(":/cb-config.toml:ro"))),
-        "config must be mounted at /cb-config.toml"
+        volumes.iter().any(|v| v.as_str() == Some(expected_mount.as_str())),
+        "config must be mounted at /cb-config.toml from {}, got {volumes:?}",
+        config.display()
     );
 
     // Required environment variables must be present.

crates/cli/src/docker_init.rs

@@ -31,6 +31,19 @@ use docker_compose_types::{
 use eyre::Result;
 use indexmap::IndexMap;
 
+/// A host path as a compose bind-mount source. Compose reads a source with no
+/// `/` or `./` prefix as a NAMED VOLUME, so a relative path needs the prefix;
+/// an absolute one must be passed through, or it is resolved against the
+/// project directory and docker creates a root-owned directory there.
+fn compose_bind_source(path: &Path) -> String {
+    let source = path.display().to_string();
+    if path.is_absolute() || source.starts_with("./") || source.starts_with("../") {
+        source
+    } else {
+        format!("./{source}")
+    }
+}
+
 /// Name of the docker compose file
 pub const CB_COMPOSE_FILE: &str = "cb.docker-compose.yml";
 /// Name of the envs file
@@ -91,8 +104,8 @@ pub async fn handle_docker_init(config_path: PathBuf, output_dir: PathBuf) -> Re
     let mut service_config = ServiceCreationInfo {
         config_info: CommitBoostConfigInfo {
             config_volume: Volumes::Simple(format!(
-                "./{}:{}:ro",
-                config_path.display(),
+                "{}:{}:ro",
+                compose_bind_source(&config_path),
                 CONFIG_DEFAULT
             )),
             cb_config: CommitBoostConfig::from_file(&config_path)?,
@@ -954,6 +967,18 @@ mod tests {
 
     // --- get_env_val ---
 
+    /// Compose reads a bare source as a named volume, so a relative path keeps
+    /// the `./` prefix; an absolute one must NOT get it, or compose resolves
+    /// `.//abs/path` against the project directory and docker creates a
+    /// root-owned directory there instead of mounting the file.
+    #[test]
+    fn test_compose_bind_source_prefixes_only_relative_paths() {
+        assert_eq!(compose_bind_source(Path::new("cb-config.toml")), "./cb-config.toml");
+        assert_eq!(compose_bind_source(Path::new("./cb-config.toml")), "./cb-config.toml");
+        assert_eq!(compose_bind_source(Path::new("../cb-config.toml")), "../cb-config.toml");
+        assert_eq!(compose_bind_source(Path::new("/etc/cb/config.toml")), "/etc/cb/config.toml");
+    }
+
     #[test]
     fn test_get_env_val_returns_string_pair() {
         let (key, val) = get_env_val("MY_KEY", "my_value");