Respect path dependencies within Git dependencies (#9594)

## Summary

If a Git repository uses a `path` dependency (rather than a
`workspace`), we need to expand the path to make it relative to the Git
root.

Closes https://github.com/astral-sh/uv/issues/9516.

crates/uv-distribution/src/metadata/lowering.rs

@@ -220,6 +220,7 @@ impl LoweredRequirement {
                             }
                             let source = path_source(
                                 PathBuf::from(path),
+                                git_member,
                                 origin,
                                 project_dir,
                                 workspace.install_path(),
@@ -465,6 +466,7 @@ impl LoweredRequirement {
                             }
                             let source = path_source(
                                 PathBuf::from(path),
+                                None,
                                 RequirementOrigin::Project,
                                 dir,
                                 dir,
@@ -553,6 +555,8 @@ pub enum LoweringError {
     WorkspaceFalse,
     #[error("Editable must refer to a local directory, not a file: `{0}`")]
     EditableFile(String),
+    #[error("Git repository references local file source, but only directories are supported as transitive Git dependencies: `{0}`")]
+    GitFile(String),
     #[error(transparent)]
     ParsedUrl(#[from] ParsedUrlError),
     #[error("Path must be UTF-8: `{0}`")]
@@ -678,6 +682,7 @@ fn registry_source(
 /// Convert a path string to a file or directory source.
 fn path_source(
     path: impl AsRef<Path>,
+    git_member: Option<&GitWorkspaceMember>,
     origin: RequirementOrigin,
     project_dir: &Path,
     workspace_root: &Path,
@@ -702,6 +707,24 @@ fn path_source(
         install_path.extension().is_none()
     };
     if is_dir {
+        if let Some(git_member) = git_member {
+            let subdirectory = uv_fs::normalize_path(
+                &uv_fs::relative_to(install_path, git_member.fetch_root)
+                    .expect("Workspace member must be relative"),
+            );
+            return Ok(RequirementSource::Git {
+                repository: git_member.git_source.git.repository().clone(),
+                reference: git_member.git_source.git.reference().clone(),
+                precise: git_member.git_source.git.precise(),
+                subdirectory: if subdirectory == PathBuf::new() {
+                    None
+                } else {
+                    Some(subdirectory)
+                },
+                url,
+            });
+        }
+
         if editable {
             Ok(RequirementSource::Directory {
                 install_path,
@@ -731,6 +754,10 @@ fn path_source(
             })
         }
     } else {
+        // TODO(charlie): If a Git repo contains a source that points to a file, what should we do?
+        if git_member.is_some() {
+            return Err(LoweringError::GitFile(url.to_string()));
+        }
         if editable {
             return Err(LoweringError::EditableFile(url.to_string()));
         }

crates/uv/tests/it/sync.rs

@@ -5409,3 +5409,92 @@ fn mismatched_name_cached_wheel() -> Result<()> {
 
     Ok(())
 }
+
+/// Sync a Git repository that depends on a package within the same repository via a `path` source.
+///
+/// See: <https://github.com/astral-sh/uv/issues/9516>
+#[test]
+fn sync_git_path_dependency() -> Result<()> {
+    let context = TestContext::new("3.13");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        requires-python = ">=3.13"
+        dependencies = ["package2"]
+
+        [tool.uv.sources]
+        package2 = { git = "https://git@github.com/astral-sh/uv-path-dependency-test.git", subdirectory = "package2" }
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    "###);
+
+    let lock = context.read("uv.lock");
+
+    insta::with_settings!(
+        {
+            filters => context.filters(),
+        },
+        {
+            assert_snapshot!(
+                lock, @r###"
+            version = 1
+            requires-python = ">=3.13"
+
+            [options]
+            exclude-newer = "2024-03-25T00:00:00Z"
+
+            [[package]]
+            name = "foo"
+            version = "0.1.0"
+            source = { virtual = "." }
+            dependencies = [
+                { name = "package2" },
+            ]
+
+            [package.metadata]
+            requires-dist = [{ name = "package2", git = "https://github.com/astral-sh/uv-path-dependency-test.git?subdirectory=package2" }]
+
+            [[package]]
+            name = "package1"
+            version = "0.1.0"
+            source = { git = "https://github.com/astral-sh/uv-path-dependency-test.git?subdirectory=package1#28781b32cf1f260cdb2c8040628079eb265202bd" }
+
+            [[package]]
+            name = "package2"
+            version = "0.1.0"
+            source = { git = "https://github.com/astral-sh/uv-path-dependency-test.git?subdirectory=package2#28781b32cf1f260cdb2c8040628079eb265202bd" }
+            dependencies = [
+                { name = "package1" },
+            ]
+            "###
+            );
+        }
+    );
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    Prepared 2 packages in [TIME]
+    Installed 2 packages in [TIME]
+     + package1==0.1.0 (from git+https://github.com/astral-sh/uv-path-dependency-test.git@28781b32cf1f260cdb2c8040628079eb265202bd#subdirectory=package1)
+     + package2==0.1.0 (from git+https://github.com/astral-sh/uv-path-dependency-test.git@28781b32cf1f260cdb2c8040628079eb265202bd#subdirectory=package2)
+    "###);
+
+    Ok(())
+}