ci/internal/git/repo.go

package git

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"os/exec"
	"path/filepath"
)

// Repository represents a local Git repository.
type Repository struct {
	dir string
}

// NewRepository creates a new repository for the given directory path.
func NewRepository(dir string) (*Repository, error) {
	abs, err := filepath.Abs(dir)
	if err != nil {
		return nil, fmt.Errorf("getting absolute directory path: %w", err)
	}

	return &Repository{dir: abs}, nil
}

func (r *Repository) Dir() string {
	return r.dir
}

// ModifiedFiles return a slice of filenames that were modified since the given commit.
func (r *Repository) ModifiedFiles(ctx context.Context, commit string) ([]string, error) {
	return r.diffNameOnly(ctx, "M", commit)
}

func (r *Repository) diffNameOnly(ctx context.Context, filter, commit string) ([]string, error) {
	var files []string

	out, err := r.execGit(ctx, "diff", "--name-only", "--diff-filter="+filter, commit, "HEAD")
	if err != nil {
		return files, fmt.Errorf("running git diff command: %w (output: %s)", err, bytes.TrimSpace(out))
	}

	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		line := string(bytes.TrimSpace(scanner.Bytes()))
		if line == "" {
			continue
		}

		files = append(files, filepath.Join(r.dir, line))
	}

	return files, nil
}

func (r *Repository) execGit(ctx context.Context, arg ...string) ([]byte, error) {
	cmd := exec.CommandContext(ctx, "git", arg...)
	cmd.Dir = r.dir

	return cmd.CombinedOutput()
}