feat: Adds git client tests, restructures files.

Tests/GitClientTests/GitClientTests.swift

@@ -0,0 +1,59 @@
+import Dependencies
+import GitClient
+import ShellClient
+import Testing
+
+@Suite("GitClientTests")
+struct GitClientTests {
+
+  @Test(arguments: GitClientVersionTestArgument.testCases)
+  func testGitClient(input: GitClientVersionTestArgument) async throws {
+    let arguments = try await run {
+      @Dependency(\.gitClient) var gitClient
+      _ = try await gitClient.version(.init(style: input.style))
+    }
+    #expect(arguments == input.expected)
+  }
+
+  func run(
+    _ operation: () async throws -> Void
+  ) async throws -> [[String]] {
+    let captured = CapturedCommand()
+
+    try await withDependencies {
+      $0.asyncShellClient = .capturing(captured)
+      $0.fileClient = .noop
+      $0.gitClient = .liveValue
+    } operation: {
+      try await operation()
+    }
+    return await captured.commands.map(\.arguments)
+  }
+}
+
+struct GitClientVersionTestArgument {
+  let style: GitClient.CurrentVersionOption.Style
+  let expected: [[String]]
+
+  static let testCases: [Self] = [
+    .init(
+      style: .tag(exactMatch: true),
+      expected: [["git", "describe", "--tags", "--exact-match"]]
+    ),
+    .init(
+      style: .tag(exactMatch: false),
+      expected: [["git", "describe", "--tags"]]
+    ),
+    .init(
+      style: .branch(commitSha: false),
+      expected: [["git", "symbolic-ref", "--quiet", "--short", "HEAD"]]
+    ),
+    .init(
+      style: .branch(commitSha: true),
+      expected: [
+        ["git", "rev-parse", "--short", "HEAD"],
+        ["git", "symbolic-ref", "--quiet", "--short", "HEAD"]
+      ]
+    )
+  ]
+}