feat: Add avatar stacks (#37594)

Parse `Co-authored-by:` trailers from commit messages and surface
contributors as an avatar stack across the commit page, commits list, PR
commits tab, latest-commit row, blame, graph, and dashboard feed.

- Up to 10 visible 20px avatars, GitHub-style overlap (6px first stride,
4px between subsequent), `+N` chip for the rest.
- Label: 1 → name; 2 → `<a> and <b>`; 3+ → `<N> people` opens a Tippy
popup with all participants.
- Names and avatars link to the repo's commits-by-author search; fall
back to profile or `mailto:`.
- Trailer parsing uses `net/mail.ParseAddress`, scans only the trailing
paragraph, filters out the commit's own author/committer.
- Drops the non-standard `Co-committed-by:` emission on squash merge and
web edits.

Devtest: `/devtest/coauthor-avatars`.

Fixes #25521

----
<img width="353" height="277" alt="image"
src="https://github.com/user-attachments/assets/72092ceb-97ca-4b09-9557-0b72d3c5458e"
/>

<img width="533" height="328"
src="https://github.com/user-attachments/assets/11d0c8f8-8b3f-4f2e-9993-879f1c06bcc5"
/>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

modules/git/commit.go

@@ -11,18 +11,10 @@ import (
 	"os/exec"
 	"strings"
 
-	"gitea.dev/modules/charset"
 	"gitea.dev/modules/git/gitcmd"
 	"gitea.dev/modules/util"
 )
 
-type CommitMessage struct {
-	MessageRaw   string
-	messageUTF8  *string
-	messageTitle *string
-	messageBody  *string
-}
-
 // Commit represents a git commit.
 type Commit struct {
 	Tree // FIXME: bad design, this field can be nil if the commit is from "last commit cache"
@@ -44,30 +36,6 @@ type CommitSignature struct {
 	Payload   string
 }
 
-func (c *CommitMessage) MessageUTF8() string {
-	if c.messageUTF8 == nil {
-		bs := charset.ToUTF8(util.UnsafeStringToBytes(c.MessageRaw), charset.ConvertOpts{ErrorReplacement: []byte{'?'}})
-		c.messageUTF8 = new(util.UnsafeBytesToString(bs))
-	}
-	return *c.messageUTF8
-}
-
-func (c *CommitMessage) MessageTitle() string {
-	if c.messageTitle == nil {
-		s, _, _ := strings.Cut(strings.TrimSpace(c.MessageUTF8()), "\n")
-		c.messageTitle = new(strings.TrimSpace(s))
-	}
-	return *c.messageTitle
-}
-
-func (c *CommitMessage) MessageBody() string {
-	if c.messageBody == nil {
-		_, s, _ := strings.Cut(strings.TrimSpace(c.MessageUTF8()), "\n")
-		c.messageBody = new(strings.TrimSpace(s))
-	}
-	return *c.messageBody
-}
-
 // ParentID returns oid of n-th parent (0-based index).
 // It returns nil if no such parent exists.
 func (c *Commit) ParentID(n int) (ObjectID, error) {

modules/git/commit_message.go

@@ -0,0 +1,131 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"net/mail"
+	"regexp"
+	"strings"
+	"sync"
+
+	"gitea.dev/modules/charset"
+	"gitea.dev/modules/container"
+	"gitea.dev/modules/util"
+)
+
+// CoAuthoredByTrailer is the canonical token for the `Co-authored-by:` git trailer.
+const CoAuthoredByTrailer = "Co-authored-by"
+
+type CommitIdentity struct {
+	Name  string
+	Email string
+}
+
+// CommitMessageTrailerValues keys are all in lower-case
+type CommitMessageTrailerValues map[string][]string
+
+type CommitMessage struct {
+	MessageRaw   string
+	messageUTF8  *string
+	messageTitle *string
+	messageBody  *string
+
+	trailerValues CommitMessageTrailerValues
+
+	allParticipants []*CommitIdentity
+}
+
+func (c *CommitMessage) MessageUTF8() string {
+	if c.messageUTF8 == nil {
+		bs := charset.ToUTF8(util.UnsafeStringToBytes(c.MessageRaw), charset.ConvertOpts{ErrorReplacement: []byte{'?'}})
+		c.messageUTF8 = new(util.UnsafeBytesToString(bs))
+	}
+	return *c.messageUTF8
+}
+
+func (c *CommitMessage) MessageTitle() string {
+	if c.messageTitle == nil {
+		s, _, _ := strings.Cut(strings.TrimSpace(c.MessageUTF8()), "\n")
+		c.messageTitle = new(strings.TrimSpace(s))
+	}
+	return *c.messageTitle
+}
+
+func (c *CommitMessage) MessageBody() string {
+	if c.messageBody == nil {
+		_, s, _ := strings.Cut(strings.TrimSpace(c.MessageUTF8()), "\n")
+		c.messageBody = new(strings.TrimSpace(s))
+	}
+	return *c.messageBody
+}
+
+func (c *CommitMessage) MessageTrailer() CommitMessageTrailerValues {
+	if c.trailerValues == nil {
+		_, _, trailer := CommitMessageSplitTrailer(c.MessageUTF8())
+		c.trailerValues = CommitMessageParseTrailer(trailer)
+	}
+	return c.trailerValues
+}
+
+var commitMessageTrailerSplit = sync.OnceValue(func() *regexp.Regexp {
+	// the sep is either something like "\n---\n" or "\n\n" in the body, or at the start of the body like "---\n"
+	return regexp.MustCompile(`(?s)^(?P<content>.*?)(?P<sep>^|^\n|^-{3,}\n|\n-{3,}\n|\n\n)(?P<trailer>(?:[A-Za-z0-9][-A-Za-z0-9]*:[^\n]*\n?)*)$`)
+})
+
+func CommitMessageSplitTrailer(s string) (content, sep, trailer string) {
+	s = util.NormalizeStringEOL(s)
+	re := commitMessageTrailerSplit()
+	v := re.FindStringSubmatch(s)
+	if v == nil {
+		return s, "", ""
+	}
+	return v[re.SubexpIndex("content")], v[re.SubexpIndex("sep")], v[re.SubexpIndex("trailer")]
+}
+
+func CommitMessageParseTrailer(s string) CommitMessageTrailerValues {
+	ret := CommitMessageTrailerValues{}
+	for line := range strings.SplitSeq(util.NormalizeStringEOL(s), "\n") {
+		k, v, ok := strings.Cut(line, ":")
+		if !ok {
+			continue
+		}
+		k, v = strings.TrimSpace(k), strings.TrimSpace(v)
+		kLower := strings.ToLower(k)
+		ret[kLower] = append(ret[kLower], v)
+	}
+	return ret
+}
+
+// AllParticipantIdentities returns all the participants in the commit, the first one is the commit's author
+func (c *Commit) AllParticipantIdentities() []*CommitIdentity {
+	if c.allParticipants != nil {
+		return c.allParticipants
+	}
+
+	exclude := container.Set[string]{}
+	c.allParticipants = append(c.allParticipants, &CommitIdentity{Name: c.Author.Name, Email: c.Author.Email})
+	exclude.Add(strings.ToLower(c.Author.Email))
+
+	addParticipant := func(name, email string) {
+		if name == "" && email == "" {
+			return
+		}
+		emailLower := strings.ToLower(email)
+		if emailLower != "" && exclude.Contains(emailLower) {
+			return
+		}
+		c.allParticipants = append(c.allParticipants, &CommitIdentity{Name: name, Email: email})
+		exclude.Add(emailLower)
+	}
+	addParticipant(c.Committer.Name, c.Committer.Email)
+	for _, coAuthorValue := range c.MessageTrailer()["co-authored-by"] {
+		addr, err := mail.ParseAddress(coAuthorValue)
+		if err == nil {
+			addParticipant(addr.Name, addr.Address)
+		} else {
+			addParticipant(coAuthorValue, "")
+		}
+	}
+	return c.allParticipants
+}

modules/git/commit_message_test.go

@@ -0,0 +1,80 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCommitMessageSanitizesInvalidUTF8(t *testing.T) {
+	commit := &Commit{
+		CommitMessage: CommitMessage{MessageRaw: "title \xff\n\n\n\nbody \xff\n\n\n"},
+	}
+	assert.Equal(t, "title ÿ", commit.MessageTitle())
+	assert.Equal(t, "body ÿ", commit.MessageBody())
+	assert.Equal(t, "title ÿ\n\n\n\nbody ÿ\n\n\n", commit.MessageUTF8())
+}
+
+func TestCommitMessageTrailer(t *testing.T) {
+	cases := []struct {
+		msg, body, sep, trailer string
+	}{
+		{"", "", "", ""},
+		{"a", "a", "", ""},
+		{"a\n\nk", "a\n\nk", "", ""},
+		{"a\n\nk:v", "a", "\n\n", "k:v"},
+		{"a\n--\nk:v", "a\n--\nk:v", "", ""},
+		{"a\n---\nk:v", "a", "\n---\n", "k:v"},
+
+		{"k: v", "", "", "k: v"},
+		{"\nk:v", "", "\n", "k:v"},
+		{"\n\nk:v", "", "\n\n", "k:v"},
+
+		{"---\nk:v", "", "---\n", "k:v"},
+		{"\n---\nk:v", "", "\n---\n", "k:v"},
+		{"a:b\n---\nk:v", "a:b", "\n---\n", "k:v"},
+	}
+	for _, c := range cases {
+		body, sep, trailer := CommitMessageSplitTrailer(c.msg)
+		assert.Equal(t, c.body, body, "input=%q", c.msg)
+		assert.Equal(t, c.sep, sep, "input=%q", c.msg)
+		assert.Equal(t, c.trailer, trailer, "input=%q", c.msg)
+	}
+}
+
+func TestCommitMessageAllParticipantIdentities(t *testing.T) {
+	sig := func(n, e string) *Signature { return &Signature{Name: n, Email: e} }
+	idt := func(n, e string) *CommitIdentity { return &CommitIdentity{Name: n, Email: e} }
+	cases := []struct {
+		commit      *Commit
+		participant []*CommitIdentity
+	}{
+		{
+			&Commit{
+				Author: sig("a", "a@m.com"), Committer: sig("c", "c@m.com"),
+				CommitMessage: CommitMessage{MessageRaw: "CO-Authored-BY: x@m.com"},
+			},
+			[]*CommitIdentity{idt("a", "a@m.com"), idt("c", "c@m.com"), idt("", "x@m.com")},
+		},
+		{
+			&Commit{
+				Author: sig("a", "a@m.com"), Committer: sig("a", "A@M.com"),
+				CommitMessage: CommitMessage{MessageRaw: "CO-Authored-BY: a@m.com"},
+			},
+			[]*CommitIdentity{idt("a", "a@m.com")},
+		},
+		{
+			&Commit{
+				Author: sig("a", "a@m.com"), Committer: sig("", ""),
+				CommitMessage: CommitMessage{MessageRaw: "Co-authored-by: Full Name <X@M.com>"},
+			},
+			[]*CommitIdentity{idt("a", "a@m.com"), idt("Full Name", "X@M.com")},
+		},
+	}
+	for _, c := range cases {
+		assert.Equal(t, c.participant, c.commit.AllParticipantIdentities())
+	}
+}

modules/git/commit_test.go

@@ -159,15 +159,6 @@ ISO-8859-1`, commitFromReader.Signature.Payload)
 	assert.Equal(t, commitFromReader, commitFromReader2)
 }
 
-func TestCommitMessageSanitizesInvalidUTF8(t *testing.T) {
-	commit := &Commit{
-		CommitMessage: CommitMessage{MessageRaw: "title \xff\n\n\n\nbody \xff\n\n\n"},
-	}
-	assert.Equal(t, "title ÿ", commit.MessageTitle())
-	assert.Equal(t, "body ÿ", commit.MessageBody())
-	assert.Equal(t, "title ÿ\n\n\n\nbody ÿ\n\n\n", commit.MessageUTF8())
-}
-
 func TestHasPreviousCommit(t *testing.T) {
 	bareRepo1Path := filepath.Join(testReposDir, "repo1_bare")
 

modules/repository/commits.go

@@ -9,19 +9,15 @@ import (
 	"net/url"
 	"time"
 
-	"gitea.dev/models/avatars"
 	repo_model "gitea.dev/models/repo"
 	user_model "gitea.dev/models/user"
-	"gitea.dev/modules/cache"
-	"gitea.dev/modules/cachegroup"
 	"gitea.dev/modules/git"
 	"gitea.dev/modules/gitrepo"
-	"gitea.dev/modules/log"
-	"gitea.dev/modules/setting"
 	api "gitea.dev/modules/structs"
 )
 
 // PushCommit represents a commit in a push operation.
+// This struct is marshaled as JSON (see ActionContent2Commits)
 type PushCommit struct {
 	Sha1           string
 	Message        string
@@ -33,6 +29,7 @@ type PushCommit struct {
 }
 
 // PushCommits represents list of commits in a push operation.
+// This struct is marshaled as JSON (see ActionContent2Commits)
 type PushCommits struct {
 	Commits    []*PushCommit
 	HeadCommit *PushCommit
@@ -128,26 +125,6 @@ func (pc *PushCommits) ToAPIPayloadCommits(ctx context.Context, repo *repo_model
 	return commits, headCommit, nil
 }
 
-// AvatarLink tries to match user in database with e-mail
-// in order to show custom avatar, and falls back to general avatar link.
-func (pc *PushCommits) AvatarLink(ctx context.Context, email string) string {
-	size := avatars.DefaultAvatarPixelSize * setting.Avatar.RenderedSizeFactor
-
-	v, _ := cache.GetWithContextCache(ctx, cachegroup.EmailAvatarLink, email, func(ctx context.Context, email string) (string, error) {
-		u, err := user_model.GetUserByEmail(ctx, email)
-		if err != nil {
-			if !user_model.IsErrUserNotExist(err) {
-				log.Error("GetUserByEmail: %v", err)
-				return "", err
-			}
-			return avatars.GenerateEmailAvatarFastLink(ctx, email, size), nil
-		}
-		return u.AvatarLinkWithSize(ctx, size), nil
-	})
-
-	return v
-}
-
 // CommitToPushCommit transforms a git.Commit to PushCommit type.
 func CommitToPushCommit(commit *git.Commit) *PushCommit {
 	return &PushCommit{

modules/repository/commits_test.go

@@ -4,14 +4,12 @@
 package repository
 
 import (
-	"strconv"
 	"testing"
 	"time"
 
 	repo_model "gitea.dev/models/repo"
 	"gitea.dev/models/unittest"
 	"gitea.dev/modules/git"
-	"gitea.dev/modules/setting"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -99,38 +97,6 @@ func TestPushCommits_ToAPIPayloadCommits(t *testing.T) {
 	assert.Equal(t, []string{"readme.md"}, headCommit.Modified)
 }
 
-func TestPushCommits_AvatarLink(t *testing.T) {
-	assert.NoError(t, unittest.PrepareTestDatabase())
-
-	pushCommits := NewPushCommits()
-	pushCommits.Commits = []*PushCommit{
-		{
-			Sha1:           "abcdef1",
-			CommitterEmail: "user2@example.com",
-			CommitterName:  "User Two",
-			AuthorEmail:    "user4@example.com",
-			AuthorName:     "User Four",
-			Message:        "message1",
-		},
-		{
-			Sha1:           "abcdef2",
-			CommitterEmail: "user2@example.com",
-			CommitterName:  "User Two",
-			AuthorEmail:    "user2@example.com",
-			AuthorName:     "User Two",
-			Message:        "message2",
-		},
-	}
-
-	assert.Equal(t,
-		"/avatars/ab53a2911ddf9b4817ac01ddcd3d975f?size="+strconv.Itoa(28*setting.Avatar.RenderedSizeFactor),
-		pushCommits.AvatarLink(t.Context(), "user2@example.com"))
-
-	assert.Equal(t,
-		"/assets/img/avatar_default.png",
-		pushCommits.AvatarLink(t.Context(), "nonexistent@example.com"))
-}
-
 func TestCommitToPushCommit(t *testing.T) {
 	now := time.Now()
 	sig := &git.Signature{

modules/setting/config/value.go

@@ -78,11 +78,16 @@ func isZeroOrEmpty(v any) bool {
 	return false
 }
 
+var SkipDatabaseConfig bool
+
 func (opt *Option[T]) ValueRevision(ctx context.Context) (v T, rev int, has bool) {
 	dg := GetDynGetter()
 	if dg == nil {
 		// this is an edge case: the database is not initialized but the system setting is going to be used
 		// it should panic to avoid inconsistent config values (from config / system setting) and fix the code
+		if SkipDatabaseConfig {
+			return opt.DefaultValue(), 0, false
+		}
 		panic("no config dyn value getter")
 	}
 

modules/templates/util_render.go

@@ -10,8 +10,10 @@ import (
 	"math"
 	"net/url"
 	"regexp"
+	"slices"
 	"strings"
 
+	user_model "gitea.dev/models/gituser"
 	issues_model "gitea.dev/models/issues"
 	"gitea.dev/models/renderhelper"
 	"gitea.dev/models/repo"
@@ -22,6 +24,7 @@ import (
 	"gitea.dev/modules/log"
 	"gitea.dev/modules/markup"
 	"gitea.dev/modules/markup/markdown"
+	"gitea.dev/modules/repository"
 	"gitea.dev/modules/reqctx"
 	"gitea.dev/modules/setting"
 	"gitea.dev/modules/svg"
@@ -31,11 +34,12 @@ import (
 )
 
 type RenderUtils struct {
-	ctx reqctx.RequestContext
+	ctx         reqctx.RequestContext
+	avatarUtils *AvatarUtils
 }
 
 func NewRenderUtils(ctx reqctx.RequestContext) *RenderUtils {
-	return &RenderUtils{ctx: ctx}
+	return &RenderUtils{ctx: ctx, avatarUtils: NewAvatarUtils(ctx)}
 }
 
 // RenderCommitMessage renders commit message title (only title)
@@ -291,3 +295,134 @@ func (ut *RenderUtils) RenderUnicodeEscapeToggleTd(combined, escapeStatus *chars
 	}
 	return `<td class="lines-escape">` + ut.RenderUnicodeEscapeToggleButton(escapeStatus) + `</td>`
 }
+
+func renderAvatarStackViewEmailLink(data *user_model.AvatarStackData, email string) template.URL {
+	if data.SearchByEmailLink != "" && email != "" {
+		return template.URL(strings.ReplaceAll(data.SearchByEmailLink, "{email}", url.QueryEscape(email)))
+	}
+	return ""
+}
+
+func (ut *RenderUtils) participantHref(data *user_model.AvatarStackData, participant *user_model.CommitParticipant) template.URL {
+	if href := renderAvatarStackViewEmailLink(data, participant.GitIdentity.Email); href != "" {
+		return href
+	}
+	if participant.GiteaUser != nil {
+		return template.URL(participant.GiteaUser.HomeLink())
+	} else if participant.GitIdentity.Email != "" {
+		return template.URL("mailto:" + participant.GitIdentity.Email)
+	}
+	return ""
+}
+
+func (ut *RenderUtils) participantAvatar(participant *user_model.CommitParticipant) template.HTML {
+	if participant.GiteaUser != nil {
+		return ut.avatarUtils.Avatar(participant.GiteaUser, 20)
+	}
+	return ut.avatarUtils.AvatarByEmail(participant.GitIdentity.Email, participant.GitIdentity.Name, 20)
+}
+
+func participantName(participant *user_model.CommitParticipant) string {
+	if participant.GiteaUser != nil {
+		return participant.GiteaUser.GetDisplayName()
+	}
+	return participant.GitIdentity.Name
+}
+
+const renderAvatarStackMaxVisible = 10
+
+// AvatarStack renders overlapping avatars for the stack participants. It emits children in reverse
+// so CSS `flex-direction: row-reverse` places the primary (Participants[0]) leftmost and last-painted (on top).
+func (ut *RenderUtils) AvatarStack(data *user_model.AvatarStackData) template.HTML {
+	visible := data.Participants
+	overflow := len(visible) - renderAvatarStackMaxVisible
+	if overflow > 0 {
+		visible = visible[:renderAvatarStackMaxVisible]
+	}
+
+	var b htmlutil.HTMLBuilder
+	b.WriteHTML(`<span class="avatar-stack">`)
+	if overflow > 0 {
+		b.WriteFormat(`<span class="avatar-stack-overflow-chip tw-text-xs" aria-label="+%d more">+%d</span>`, overflow, overflow)
+	}
+
+	// FIXME: such "backward" breaks a11y like screen readers
+	for _, participant := range slices.Backward(visible) {
+		ut.writeAvatarStackItem(&b, data, participant)
+	}
+	b.WriteHTML(`</span>`)
+	return b.HTMLString()
+}
+
+func (ut *RenderUtils) writeAvatarStackItem(b *htmlutil.HTMLBuilder, data *user_model.AvatarStackData, participant *user_model.CommitParticipant) {
+	avatar := ut.participantAvatar(participant)
+	if href := ut.participantHref(data, participant); href != "" {
+		b.WriteFormat(`<a href="%s">%s</a>`, href, avatar)
+	} else {
+		b.WriteFormat(`<span>%s</span>`, avatar)
+	}
+}
+
+func (ut *RenderUtils) AvatarStackPushCommit(pushCommit *repository.PushCommit) template.HTML {
+	fakeGitCommit := git.Commit{
+		CommitMessage: git.CommitMessage{MessageRaw: pushCommit.Message},
+		Author:        &git.Signature{Name: pushCommit.AuthorName, Email: pushCommit.AuthorEmail},
+		// there is no way to know the real committer, but the field can't be nil
+		Committer: &git.Signature{Name: pushCommit.AuthorName, Email: pushCommit.AuthorEmail},
+	}
+	data := user_model.BuildAvatarStackData(ut.ctx, fakeGitCommit.AllParticipantIdentities(), nil)
+	return ut.AvatarStack(data)
+}
+
+// AvatarStackWithNames renders the avatar stack plus a label: `name` / `a and b` / `N people` (opens popup).
+func (ut *RenderUtils) AvatarStackWithNames(data *user_model.AvatarStackData) template.HTML {
+	locale := ut.ctx.Value(translation.ContextKey).(translation.Locale)
+	participants := data.Participants
+
+	var b htmlutil.HTMLBuilder
+	b.WriteHTML(`<span class="avatar-stack-names">`)
+	b.WriteHTML(ut.AvatarStack(data))
+
+	switch len(participants) {
+	case 1:
+		b.WriteHTML(ut.participantNameLink(data, participants[0]))
+	case 2:
+		b.WriteHTML(ut.participantNameLink(data, participants[0]))
+		b.WriteFormat(`<span>%s</span>`, locale.Tr("repo.commits.avatar_stack_and"))
+		b.WriteHTML(ut.participantNameLink(data, participants[1]))
+	default:
+		b.WriteFormat(`<button type="button" class="avatar-stack-popup-trigger" data-global-init="initAvatarStackPopup">%s</button>`,
+			locale.Tr("repo.commits.avatar_stack_people", len(participants)))
+		b.WriteHTML(`<div class="tippy-target"><div class="avatar-stack-popup">`)
+		for _, participant := range participants {
+			b.WriteHTML(ut.participantPopupRow(data, participant))
+		}
+		b.WriteHTML(`</div></div>`)
+	}
+
+	b.WriteHTML(`</span>`)
+	return b.HTMLString()
+}
+
+// participantNameLink prefers (in order): commits-by-author search, `GetShortDisplayNameLinkHTML` (keeps alt-name tooltip), `mailto:`, bare name.
+func (ut *RenderUtils) participantNameLink(data *user_model.AvatarStackData, participant *user_model.CommitParticipant) template.HTML {
+	if href := renderAvatarStackViewEmailLink(data, participant.GitIdentity.Email); href != "" {
+		return htmlutil.HTMLFormat(`<a class="muted" href="%s">%s</a>`, href, participantName(participant))
+	}
+	if participant.GiteaUser != nil {
+		return participant.GiteaUser.GetShortDisplayNameLinkHTML()
+	}
+	if participant.GitIdentity.Email != "" {
+		return htmlutil.HTMLFormat(`<a class="muted" href="mailto:%s">%s</a>`, participant.GitIdentity.Email, participant.GitIdentity.Name)
+	}
+	return template.HTML(template.HTMLEscapeString(participant.GitIdentity.Name))
+}
+
+func (ut *RenderUtils) participantPopupRow(data *user_model.AvatarStackData, participant *user_model.CommitParticipant) template.HTML {
+	avatar := ut.participantAvatar(participant)
+	name := participantName(participant)
+	if href := ut.participantHref(data, participant); href != "" {
+		return htmlutil.HTMLFormat(`<a class="silenced flex-text-block" href="%s">%s<span>%s</span></a>`, href, avatar, name)
+	}
+	return htmlutil.HTMLFormat(`<span class="flex-text-block">%s<span>%s</span></span>`, avatar, name)
+}

modules/templates/util_render_test.go

@@ -7,15 +7,19 @@ import (
 	"context"
 	"html/template"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 
+	"gitea.dev/models/gituser"
 	"gitea.dev/models/issues"
 	"gitea.dev/models/repo"
 	user_model "gitea.dev/models/user"
+	"gitea.dev/modules/git"
 	"gitea.dev/modules/markup"
 	"gitea.dev/modules/reqctx"
 	"gitea.dev/modules/setting"
+	"gitea.dev/modules/setting/config"
 	"gitea.dev/modules/test"
 	"gitea.dev/modules/translation"
 
@@ -298,3 +302,52 @@ func TestUserMention(t *testing.T) {
 	rendered := newTestRenderUtils(t).MarkdownToHtml("@no-such-user @mention-user @mention-user")
 	assert.Equal(t, `<p>@no-such-user <a href="/mention-user" rel="nofollow">@mention-user</a> <a href="/mention-user" rel="nofollow">@mention-user</a></p>`, strings.TrimSpace(string(rendered)))
 }
+
+func TestAvatarStack(t *testing.T) {
+	defer test.MockVariableValue(&config.SkipDatabaseConfig, true)()
+
+	ut := newTestRenderUtils(t)
+	mkCo := func(name, email string) *git.CommitIdentity {
+		return &git.CommitIdentity{Name: name, Email: email}
+	}
+	authorSig := mkCo("Alice", "alice@example.com")
+	mkData := func(co ...*git.CommitIdentity) *gituser.AvatarStackData {
+		all := append([]*git.CommitIdentity{authorSig}, co...)
+		return gituser.BuildAvatarStackData(t.Context(), all, &user_model.EmailUserMap{})
+	}
+
+	t.Run("lone author renders bare name, no label", func(t *testing.T) {
+		got := string(ut.AvatarStackWithNames(mkData()))
+		assert.Contains(t, got, `<span class="avatar-stack-names">`)
+		assert.Contains(t, got, "Alice")
+		assert.NotContains(t, got, "avatar_stack_and")
+		assert.NotContains(t, got, "avatar_stack_people")
+	})
+
+	t.Run("two participants use and label", func(t *testing.T) {
+		got := string(ut.AvatarStackWithNames(mkData(mkCo("Bob", "bob@example.com"))))
+		assert.Contains(t, got, "repo.commits.avatar_stack_and")
+		assert.Contains(t, got, "Bob")
+		assert.NotContains(t, got, "avatar_stack_people")
+		assert.Contains(t, got, `<span class="avatar-stack">`)
+	})
+
+	t.Run("three participants switch to N people label with tippy popup", func(t *testing.T) {
+		got := string(ut.AvatarStackWithNames(mkData(mkCo("Bob", "bob@example.com"), mkCo("Carol", "carol@example.com"))))
+		assert.Contains(t, got, "repo.commits.avatar_stack_people:3")
+		assert.NotContains(t, got, "repo.commits.avatar_stack_and")
+		assert.Contains(t, got, `data-global-init="initAvatarStackPopup"`)
+		assert.Contains(t, got, `<div class="tippy-target">`)
+		assert.Contains(t, got, `class="avatar-stack-popup"`)
+	})
+
+	t.Run("overflow chip renders beyond 10 participants", func(t *testing.T) {
+		cos := make([]*git.CommitIdentity, 0, renderAvatarStackMaxVisible+1)
+		for i := range renderAvatarStackMaxVisible + 1 {
+			cos = append(cos, mkCo("X", strconv.Itoa(i)+"@example.com"))
+		}
+		got := ut.AvatarStack(gituser.BuildAvatarStackData(t.Context(), cos, &user_model.EmailUserMap{}))
+		assert.Contains(t, got, `class="avatar-stack-overflow-chip`)
+		assert.Contains(t, got, "+1")
+	})
+}