perf(changelog): improve changelog sort performance (#5161)

This commit removes the unnecessary slice copy in `sortEntries`, and
replaces `sort.Slice` [^1] with the new `slices.SortFunc` [^2].

As recommended by the Go documentation, `slices.SortFunc` is generally
faster because it uses generic, whereas `sort.Slice` relies on
reflection, which incurs additional allocations

The benchmark result from the newly added `Benchmark_sortEntries` show
approximately a 64% performance improvement.


Benchmark result:

```
                     │   old.txt    │               new.txt               │
                     │    sec/op    │   sec/op     vs base                │
_sortEntries/asc-16    16.458µ ± 1%   5.958µ ± 1%  -63.80% (p=0.000 n=10)
_sortEntries/desc-16   17.675µ ± 1%   6.020µ ± 0%  -65.94% (p=0.000 n=10)
geomean                 17.06µ        5.989µ       -64.89%

                     │   old.txt    │               new.txt                │
                     │     B/op     │     B/op      vs base                │
_sortEntries/asc-16    3.164Ki ± 0%   1.164Ki ± 0%  -63.21% (p=0.000 n=10)
_sortEntries/desc-16   3.422Ki ± 0%   1.164Ki ± 0%  -65.98% (p=0.000 n=10)
geomean                3.290Ki        1.164Ki       -64.62%

                     │  old.txt   │              new.txt               │
                     │ allocs/op  │ allocs/op   vs base                │
_sortEntries/asc-16    68.00 ± 0%   25.00 ± 0%  -63.24% (p=0.000 n=10)
_sortEntries/desc-16   72.00 ± 0%   25.00 ± 0%  -65.28% (p=0.000 n=10)
geomean                69.97        25.00       -64.27%
```

[^1]: https://pkg.go.dev/sort#Slice
[^2]: https://pkg.go.dev/slices#SortFunc

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

internal/pipe/changelog/changelog.go

@@ -2,12 +2,13 @@
 package changelog
 
 import (
+	"cmp"
 	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
 	"regexp"
-	"sort"
+	"slices"
 	"strings"
 
 	"github.com/caarlos0/log"
@@ -211,7 +212,7 @@ func formatChangelog(ctx *context.Context, entries []string) (string, error) {
 		}
 	}
 
-	sort.Slice(groups, groupSort(groups))
+	slices.SortFunc(groups, groupSort)
 	for _, group := range groups {
 		if len(group.entries) > 0 {
 			result = append(result, group.title)
@@ -221,10 +222,8 @@ func formatChangelog(ctx *context.Context, entries []string) (string, error) {
 	return strings.Join(result, newLineFor(ctx)), nil
 }
 
-func groupSort(groups []changelogGroup) func(i, j int) bool {
-	return func(i, j int) bool {
-		return groups[i].order < groups[j].order
-	}
+func groupSort(i, j changelogGroup) int {
+	return cmp.Compare(i.order, j.order)
 }
 
 func filterAndPrefixItems(ss []string) []string {
@@ -306,17 +305,16 @@ func sortEntries(ctx *context.Context, entries []string) []string {
 	if direction == "" {
 		return entries
 	}
-	result := make([]string, len(entries))
-	copy(result, entries)
-	sort.Slice(result, func(i, j int) bool {
-		imsg := extractCommitInfo(result[i])
-		jmsg := extractCommitInfo(result[j])
+	slices.SortFunc(entries, func(i, j string) int {
+		imsg := extractCommitInfo(i)
+		jmsg := extractCommitInfo(j)
+		compareRes := strings.Compare(imsg, jmsg)
 		if direction == "asc" {
-			return strings.Compare(imsg, jmsg) < 0
+			return compareRes
 		}
-		return strings.Compare(imsg, jmsg) > 0
+		return -compareRes
 	})
-	return result
+	return entries
 }
 
 func keep(filter *regexp.Regexp, entries []string) (result []string) {

internal/pipe/changelog/changelog_test.go

@@ -9,14 +9,13 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/require"
-
 	"github.com/goreleaser/goreleaser/v2/internal/client"
 	"github.com/goreleaser/goreleaser/v2/internal/git"
 	"github.com/goreleaser/goreleaser/v2/internal/testctx"
 	"github.com/goreleaser/goreleaser/v2/internal/testlib"
 	"github.com/goreleaser/goreleaser/v2/pkg/config"
 	"github.com/goreleaser/goreleaser/v2/pkg/context"
+	"github.com/stretchr/testify/require"
 )
 
 func TestDescription(t *testing.T) {
@@ -289,6 +288,33 @@ func TestChangelogSort(t *testing.T) {
 	}
 }
 
+func Benchmark_sortEntries(b *testing.B) {
+	ctx := testctx.New()
+	entries := []string{
+		"added feature 1",
+		"fixed bug 2",
+		"ignored: whatever",
+		"docs: whatever",
+		"something about cArs we dont need",
+		"feat: added that thing",
+		"Merge pull request #999 from goreleaser/some-branch",
+		"this is not a Merge pull request",
+	}
+
+	b.Run("asc", func(b *testing.B) {
+		ctx.Config.Changelog.Sort = "asc"
+		for range b.N {
+			sortEntries(ctx, entries)
+		}
+	})
+	b.Run("desc", func(b *testing.B) {
+		ctx.Config.Changelog.Sort = "desc"
+		for range b.N {
+			sortEntries(ctx, entries)
+		}
+	})
+}
+
 func TestChangelogInvalidSort(t *testing.T) {
 	ctx := testctx.NewWithCfg(config.Project{
 		Changelog: config.Changelog{
@@ -814,12 +840,23 @@ func TestGroup(t *testing.T) {
 		},
 	}, testctx.WithCurrentTag("v0.0.2"), withFirstCommit(t))
 	require.NoError(t, Pipe{}.Run(ctx))
-	require.Contains(t, ctx.ReleaseNotes, "## Changelog")
-	require.Contains(t, ctx.ReleaseNotes, "### Bots")
-	require.Contains(t, ctx.ReleaseNotes, "### Features")
-	require.Contains(t, ctx.ReleaseNotes, "### Bug Fixes")
-	require.NotContains(t, ctx.ReleaseNotes, "### Catch nothing")
-	require.Contains(t, ctx.ReleaseNotes, "### Others")
+	require.Regexp(t, `## Changelog
+### Features
+\* \w+ feat: added that thing
+### Bug Fixes
+\* \w+ bug: Merge pull request #999 from goreleaser\/some-branch
+### Bots
+\* \w+ feat\(deps\): update foobar \[bot\]
+### Others
+\* \w+ first
+\* \w+ this is not a Merge pull request
+\* \w+ chore: something about cArs we dont need
+\* \w+ docs: whatever
+\* \w+ fix: whatever
+\* \w+ ignored: whatever
+\* \w+ fixed bug 2
+\* \w+ added feature 1
+`, ctx.ReleaseNotes)
 }
 
 func TestGroupBadRegex(t *testing.T) {