chore: import upstream snapshot with attribution

internal/qualitygate/diff/diff.go

@@ -0,0 +1,133 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package diff
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"sort"
+	"strings"
+)
+
+var ErrFileAtRevisionMissing = errors.New("file missing at revision")
+
+type Scope struct {
+	Global    bool
+	AllSkills map[string]bool
+	Files     map[string]bool
+}
+
+func ChangedFiles(ctx context.Context, repo, from string) ([]string, error) {
+	if from == "" {
+		return nil, nil
+	}
+	return gitChangedFiles(ctx, repo, "diff", "--name-only", "-z", "--diff-filter=ACMRD", from+"...HEAD")
+}
+
+func ChangedFilesIncludingWorktree(ctx context.Context, repo, from string) ([]string, error) {
+	var all []string
+	if from != "" {
+		committed, err := ChangedFiles(ctx, repo, from)
+		if err != nil {
+			return nil, err
+		}
+		all = append(all, committed...)
+	}
+	for _, args := range [][]string{
+		{"diff", "--name-only", "-z", "--diff-filter=ACMRD"},
+		{"diff", "--cached", "--name-only", "-z", "--diff-filter=ACMRD"},
+		{"ls-files", "--others", "--exclude-standard", "-z"},
+	} {
+		files, err := gitChangedFiles(ctx, repo, args...)
+		if err != nil {
+			return nil, err
+		}
+		all = append(all, files...)
+	}
+	return uniqueSorted(all), nil
+}
+
+func gitChangedFiles(ctx context.Context, repo string, args ...string) ([]string, error) {
+	cmd := exec.CommandContext(ctx, "git", args...)
+	cmd.Dir = repo
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, fmt.Errorf("git %s changed files: %w", strings.Join(args, " "), err)
+	}
+	// Output is NUL-delimited (-z) so paths containing whitespace stay intact.
+	var lines []string
+	for _, name := range strings.Split(string(out), "\x00") {
+		if name != "" {
+			lines = append(lines, name)
+		}
+	}
+	sort.Strings(lines)
+	return lines, nil
+}
+
+func uniqueSorted(files []string) []string {
+	if len(files) == 0 {
+		return nil
+	}
+	sort.Strings(files)
+	out := files[:0]
+	var last string
+	for i, file := range files {
+		if i > 0 && file == last {
+			continue
+		}
+		out = append(out, file)
+		last = file
+	}
+	return out
+}
+
+func FileAtRevision(ctx context.Context, repo, rev, path string) ([]byte, error) {
+	cmd := exec.CommandContext(ctx, "git", "show", rev+":"+path)
+	cmd.Dir = repo
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		if isFileAtRevisionMissing(string(out)) {
+			return nil, ErrFileAtRevisionMissing
+		}
+		return nil, fmt.Errorf("git show %s:%s: %w", rev, path, err)
+	}
+	return out, nil
+}
+
+func isFileAtRevisionMissing(stderr string) bool {
+	return strings.Contains(stderr, "exists on disk, but not in") ||
+		strings.Contains(stderr, "does not exist in")
+}
+
+func FromChangedFiles(files []string) Scope {
+	scope := Scope{AllSkills: map[string]bool{}, Files: map[string]bool{}}
+	for _, file := range files {
+		scope.Files[file] = true
+		parts := strings.Split(file, "/")
+		if len(parts) >= 2 && parts[0] == "skills" {
+			scope.AllSkills[parts[1]] = true
+			continue
+		}
+		if strings.HasPrefix(file, "cmd/") ||
+			strings.HasPrefix(file, "shortcuts/") ||
+			strings.HasPrefix(file, "internal/output/") ||
+			strings.HasPrefix(file, "internal/errclass/") ||
+			strings.HasPrefix(file, "errs/") {
+			scope.Global = true
+		}
+	}
+	return scope
+}
+
+func ChangedUnder(files map[string]bool, prefix string) bool {
+	for file := range files {
+		if strings.HasPrefix(file, prefix) {
+			return true
+		}
+	}
+	return false
+}