feat: Move git clone management to a seperate API (#58)

# What?

Migrates the git clone component of the git strategy into a separate API

# Why?

Experimentation on implementing private repo support for the gomod
strategy in #56 revealed we are
likely better off separating the git clone behaviour so that it can be
shared between multiple strategies.

Author: js-murph

internal/strategy/git/command.go internal/gitclone/command.gointernal/strategy/git/command.go renamed to internal/gitclone/command.go

@@ -1,4 +1,6 @@
-package git
+// Package gitclone provides reusable git clone management with lifecycle control,
+// concurrency management, and large repository optimizations.
+package gitclone
 
 import (
 	"bufio"
@@ -9,8 +11,6 @@ import (
 	"github.com/alecthomas/errors"
 )
 
-// gitCommand creates a git command with insteadOf URL rewriting disabled for the given URL
-// to prevent infinite loops where git config rules rewrite URLs to point back through the proxy.
 func gitCommand(ctx context.Context, url string, args ...string) (*exec.Cmd, error) {
 	configArgs, err := getInsteadOfDisableArgsForURL(ctx, url)
 	if err != nil {
@@ -27,7 +27,6 @@ func gitCommand(ctx context.Context, url string, args ...string) (*exec.Cmd, err
 	return cmd, nil
 }
 
-// getInsteadOfDisableArgsForURL returns arguments to disable insteadOf rules that would affect the given URL.
 func getInsteadOfDisableArgsForURL(ctx context.Context, targetURL string) ([]string, error) {
 	if targetURL == "" {
 		return nil, nil
@@ -36,7 +35,6 @@ func getInsteadOfDisableArgsForURL(ctx context.Context, targetURL string) ([]str
 	cmd := exec.CommandContext(ctx, "git", "config", "--get-regexp", "^url\\..*\\.(insteadof|pushinsteadof)$")
 	output, err := cmd.CombinedOutput()
 	if err != nil {
-		// Exit code 1 when no insteadOf rules exist is expected, not an error
 		return []string{}, nil //nolint:nilerr
 	}
 
@@ -60,3 +58,18 @@ func getInsteadOfDisableArgsForURL(ctx context.Context, targetURL string) ([]str
 
 	return args, nil
 }
+
+func ParseGitRefs(output []byte) map[string]string {
+	refs := make(map[string]string)
+	scanner := bufio.NewScanner(strings.NewReader(string(output)))
+	for scanner.Scan() {
+		line := scanner.Text()
+		parts := strings.Fields(line)
+		if len(parts) >= 2 {
+			sha := parts[0]
+			ref := parts[1]
+			refs[ref] = sha
+		}
+	}
+	return refs
+}

internal/strategy/git/command_test.go internal/gitclone/command_test.gointernal/strategy/git/command_test.go renamed to internal/gitclone/command_test.go

@@ -1,4 +1,4 @@
-package git //nolint:testpackage // Internal functions need to be tested
+package gitclone //nolint:testpackage // Internal functions need to be tested
 
 import (
 	"context"
@@ -13,9 +13,7 @@ func TestGetInsteadOfDisableArgsForURL(t *testing.T) {
 	tests := []struct {
 		name      string
 		targetURL string
-		// We can't easily test the actual git config reading in a unit test,
-		// but we can test the logic would work correctly
-		skipTest bool
+		skipTest  bool
 	}{
 		{
 			name:      "EmptyURL",
@@ -47,12 +45,10 @@ func TestGetInsteadOfDisableArgsForURL(t *testing.T) {
 func TestGitCommand(t *testing.T) {
 	ctx := context.Background()
 
-	// Test that gitCommand creates a valid command
 	cmd, err := gitCommand(ctx, "https://github.com/user/repo", "version")
 	assert.NoError(t, err)
 
 	assert.NotZero(t, cmd)
-	// Should have at least "git" and "version" in args
 	assert.True(t, len(cmd.Args) >= 2)
 	// First arg should be git binary path
 	assert.Equal(t, "git", cmd.Args[0])
@@ -63,7 +59,6 @@ func TestGitCommand(t *testing.T) {
 func TestGitCommandWithEmptyURL(t *testing.T) {
 	ctx := context.Background()
 
-	// Test with empty URL (for commands that don't need URL filtering)
 	cmd, err := gitCommand(ctx, "", "version")
 	assert.NoError(t, err)