feat(platform): add GitClient helper with idempotent EnsureRepo

internal/platform/git.go

@@ -0,0 +1,23 @@
+package platform
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+)
+
+// GitClient wraps `git` via a Runner.
+type GitClient struct{ Runner Runner }
+
+// Clone always runs `git clone --depth=1 url dest`.
+func (g GitClient) Clone(ctx context.Context, url, dest string) error {
+	return g.Runner.Run(ctx, "git", "clone", "--depth=1", url, dest)
+}
+
+// EnsureRepo clones url into dest if dest/.git is missing; otherwise noop.
+func (g GitClient) EnsureRepo(ctx context.Context, url, dest string) error {
+	if _, err := os.Stat(filepath.Join(dest, ".git")); err == nil {
+		return nil
+	}
+	return g.Clone(ctx, url, dest)
+}

internal/platform/git_test.go

@@ -0,0 +1,55 @@
+package platform
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+type gitFakeRunner struct {
+	calls [][]string
+	err   error
+}
+
+func (f *gitFakeRunner) Run(_ context.Context, name string, args ...string) error {
+	f.calls = append(f.calls, append([]string{name}, args...))
+	return f.err
+}
+func (f *gitFakeRunner) Output(_ context.Context, name string, args ...string) ([]byte, error) {
+	return nil, nil
+}
+
+func TestGitEnsureRepoClonesWhenMissing(t *testing.T) {
+	r := &gitFakeRunner{}
+	g := GitClient{Runner: r}
+	dest := filepath.Join(t.TempDir(), "repo")
+	if err := g.EnsureRepo(context.Background(), "https://x/y.git", dest); err != nil {
+		t.Fatal(err)
+	}
+	if len(r.calls) != 1 {
+		t.Fatalf("want 1 call, got %d: %v", len(r.calls), r.calls)
+	}
+	got := r.calls[0]
+	want := []string{"git", "clone", "--depth=1", "https://x/y.git", dest}
+	for i := range want {
+		if i >= len(got) || got[i] != want[i] {
+			t.Fatalf("call = %v, want %v", got, want)
+		}
+	}
+}
+
+func TestGitEnsureRepoSkipsWhenPresent(t *testing.T) {
+	dest := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dest, ".git"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	r := &gitFakeRunner{}
+	g := GitClient{Runner: r}
+	if err := g.EnsureRepo(context.Background(), "https://x/y.git", dest); err != nil {
+		t.Fatal(err)
+	}
+	if len(r.calls) != 0 {
+		t.Fatalf("expected no calls, got %v", r.calls)
+	}
+}