fix(ui): too many participants shown in commit avatar stacks (#38689) (#38700)

Backport #38689

Show only author and co-authors without committer, and deduplicate the
same user with multiple email addresses.

The commit list "Author" column should not show the committer. This is
somewhat misleading, and arguably showing it on the individual commit
page is sufficient and consistent with other forges.

The same user with multiple email addresses often happens when
DEFAULT_KEEP_EMAIL_PRIVATE is enabled and Gitea does not use an actual
email address by default for edits. Showing the same avatar and name
twice is not helpful then.

Ref #37594
Fix #38488

Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/gituser/avatar_stack.go

@@ -7,6 +7,7 @@ import (
 	"context"
 
 	"gitea.dev/models/user"
+	"gitea.dev/modules/container"
 	"gitea.dev/modules/git"
 	"gitea.dev/modules/log"
 )
@@ -33,11 +34,18 @@ func BuildAvatarStackData(ctx context.Context, allParticipants []*git.CommitIden
 	ret := &AvatarStackData{
 		Participants: make([]*CommitParticipant, 0, len(allParticipants)),
 	}
+	uniqueUserIDs := make(container.Set[int64])
 	for _, p := range allParticipants {
 		var giteaUser *user.User
 		if emailUserMap != nil {
 			giteaUser = emailUserMap.GetByEmail(p.Email)
 		}
+		if giteaUser != nil {
+			// identities without a Gitea account can only be compared by their git identity
+			if !uniqueUserIDs.Add(giteaUser.ID) {
+				continue
+			}
+		}
 		ret.Participants = append(ret.Participants, &CommitParticipant{GiteaUser: giteaUser, GitIdentity: p})
 	}
 	return ret

models/gituser/gituser.go

@@ -39,8 +39,7 @@ func GetUserCommitsByGitCommits(ctx context.Context, gitCommits []*git.Commit, r
 	emailSet := make(container.Set[string])
 	for _, c := range gitCommits {
 		emailSet.Add(c.Author.Email)
-		emailSet.Add(c.Committer.Email)
-		for _, p := range c.AllParticipantIdentities() {
+		for _, p := range c.AllAuthorIdentities() {
 			emailSet.Add(p.Email)
 		}
 	}
@@ -55,7 +54,7 @@ func GetUserCommitsByGitCommits(ctx context.Context, gitCommits []*git.Commit, r
 		uc := &UserCommit{
 			AuthorUser:      emailUserMap.GetByEmail(c.Author.Email), // FIXME: why GetUserCommitsByGitCommits uses "Author", but ParseCommitsWithSignature uses "Committer"?
 			GitCommit:       c,
-			AvatarStackData: BuildAvatarStackData(ctx, c.AllParticipantIdentities(), emailUserMap),
+			AvatarStackData: BuildAvatarStackData(ctx, c.AllAuthorIdentities(), emailUserMap),
 		}
 		uc.AvatarStackData.SearchByEmailLink = searchByEmailLink
 		userCommits = append(userCommits, uc)