Branch list enhancements (woodpecker-ci#808)

* Allow users not logged in to access branches page
  (fixes a nil pointer derefernce)

* Add Gogs support for branches

server/remote/gitea/gitea.go

@@ -423,7 +423,11 @@ func (c *Gitea) Deactivate(ctx context.Context, u *model.User, r *model.Repo, li
 
 // Branches returns the names of all branches for the named repository.
 func (c *Gitea) Branches(ctx context.Context, u *model.User, r *model.Repo) ([]string, error) {
-	client, err := c.newClientToken(ctx, u.Token)
+	token := ""
+	if u != nil {
+		token = u.Token
+	}
+	client, err := c.newClientToken(ctx, token)
 	if err != nil {
 		return nil, err
 	}

server/remote/github/github.go

@@ -458,7 +458,11 @@ func (c *client) Activate(ctx context.Context, u *model.User, r *model.Repo, lin
 
 // Branches returns the names of all branches for the named repository.
 func (c *client) Branches(ctx context.Context, u *model.User, r *model.Repo) ([]string, error) {
-	client := c.newClientToken(ctx, u.Token)
+	token := ""
+	if u != nil {
+		token = u.Token
+	}
+	client := c.newClientToken(ctx, token)
 
 	githubBranches, _, err := client.Repositories.ListBranches(ctx, r.Owner, r.Name, &github.BranchListOptions{})
 	if err != nil {

server/remote/gitlab/gitlab.go

@@ -488,7 +488,11 @@ func (g *Gitlab) Deactivate(ctx context.Context, user *model.User, repo *model.R
 
 // Branches returns the names of all branches for the named repository.
 func (g *Gitlab) Branches(ctx context.Context, user *model.User, repo *model.Repo) ([]string, error) {
-	client, err := newClient(g.URL, user.Token, g.SkipVerify)
+	token := ""
+	if user != nil {
+		token = user.Token
+	}
+	client, err := newClient(g.URL, token, g.SkipVerify)
 	if err != nil {
 		return nil, err
 	}

server/remote/gogs/gogs.go

@@ -262,8 +262,21 @@ func (c *client) Deactivate(ctx context.Context, u *model.User, r *model.Repo, l
 
 // Branches returns the names of all branches for the named repository.
 func (c *client) Branches(ctx context.Context, u *model.User, r *model.Repo) ([]string, error) {
-	// TODO: fetch all branches
-	return []string{r.Branch}, nil
+	token := ""
+	if u != nil {
+		token = u.Token
+	}
+	client := c.newClientToken(token)
+	gogsBranches, err := client.ListRepoBranches(r.Owner, r.Name)
+	if err != nil {
+		return nil, err
+	}
+
+	branches := make([]string, 0)
+	for _, branch := range gogsBranches {
+		branches = append(branches, branch.Name)
+	}
+	return branches, nil
 }
 
 // Hook parses the incoming Gogs hook and returns the Repository and Build