Add Git commit hash to the revision field of component metadata

Cargo.toml

@@ -23,6 +23,7 @@ bytes = { workspace = true }
 cargo_metadata = { workspace = true }
 cargo-component-core = { workspace = true }
 cargo-config2 = { workspace = true }
+git2 = { workspace = true }
 clap = { workspace = true }
 futures = { workspace = true }
 heck = { workspace = true }
@@ -74,6 +75,7 @@ bytes = "1.6.0"
 cargo_metadata = "0.19.1"
 cargo-component-core = { path = "crates/core", version = "0.21.1" }
 cargo-config2 = "0.1.24"
+git2 = "0.20.1"
 clap = { version = "4.5.4", features = ["derive", "env"] }
 dirs = "5"
 futures = "0.3.30"

src/git.rs

@@ -0,0 +1,51 @@
+use anyhow::Result;
+use cargo_metadata::Package;
+use git2::{ErrorClass, ErrorCode, Repository};
+
+#[derive(Debug)]
+pub struct GitMetadata {
+    commit: String,
+}
+
+impl GitMetadata {
+    /// Creates a new Git metadata for the given cargo package.
+    pub fn from_package(package: &Package) -> Result<Option<Self>> {
+        log::debug!(
+            "searching for git metadata from manifest `{path}`",
+            path = package.manifest_path
+        );
+
+        let repository = match Repository::discover(package.manifest_path.clone()) {
+            Ok(repository) => Ok(repository),
+            Err(ref e)
+                if e.class() == ErrorClass::Repository && e.code() == ErrorCode::NotFound =>
+            {
+                return Ok(None)
+            }
+            Err(e) => Err(e),
+        }?;
+
+        let head = match repository.head() {
+            Ok(head) => Ok(head),
+            Err(ref e)
+                if e.class() == ErrorClass::Reference && e.code() == ErrorCode::UnbornBranch =>
+            {
+                return Ok(None)
+            }
+            Err(error) => Err(error),
+        }?;
+
+        let commit = head.peel_to_commit()?;
+        let commit_id = commit.id();
+
+        let metadata = Self {
+            commit: commit_id.to_string(),
+        };
+
+        Ok(Some(metadata))
+    }
+
+    pub fn commit(&self) -> &str {
+        &self.commit
+    }
+}

src/lib.rs

@@ -36,6 +36,7 @@ use wit_component::ComponentEncoder;
 use crate::target::install_wasm32_wasip1;
 
 use config::{CargoArguments, CargoPackageSpec, Config};
+use git::GitMetadata;
 use lock::{acquire_lock_file_ro, acquire_lock_file_rw};
 use metadata::ComponentMetadata;
 use registry::{PackageDependencyResolution, PackageResolutionMap};
@@ -44,6 +45,7 @@ mod bindings;
 pub mod commands;
 pub mod config;
 mod generator;
+mod git;
 mod lock;
 mod metadata;
 mod registry;
@@ -971,12 +973,14 @@ fn componentize(
         .validate(true);
 
     let package = &cargo_metadata[&artifact.package_id];
-    let component = add_component_metadata(&package, &encoder.encode()?).with_context(|| {
-        format!(
-            "failed to add metadata to output component `{path}`",
-            path = path.display()
-        )
-    })?;
+    let git = GitMetadata::from_package(package)?;
+    let component = add_component_metadata(package, git.as_ref(), &encoder.encode()?)
+        .with_context(|| {
+            format!(
+                "failed to add metadata to output component `{path}`",
+                path = path.display()
+            )
+        })?;
 
     // To make the write atomic, first write to a temp file and then rename the file
     let temp_dir = cargo_metadata.target_directory.join("tmp");
@@ -1021,7 +1025,11 @@ pub struct PublishOptions<'a> {
 }
 
 /// Read metadata from `Cargo.toml` and add it to the component
-fn add_component_metadata(package: &Package, wasm: &[u8]) -> Result<Vec<u8>> {
+fn add_component_metadata(
+    package: &Package,
+    git: Option<&GitMetadata>,
+    wasm: &[u8],
+) -> Result<Vec<u8>> {
     let metadata = wasm_metadata::AddMetadata {
         name: Some(package.name.clone()),
         language: vec![("Rust".to_string(), "".to_string())],
@@ -1055,8 +1063,7 @@ fn add_component_metadata(package: &Package, wasm: &[u8]) -> Result<Vec<u8>> {
             .as_ref()
             .map(|s| wasm_metadata::Homepage::new(s.to_string().as_str()))
             .transpose()?,
-        // TODO: get the git commit hash
-        revision: None,
+        revision: git.map(|git| wasm_metadata::Revision::new(git.commit().to_string())),
         version: Some(wasm_metadata::Version::new(package.version.to_string())),
     };
     metadata.to_wasm(wasm)