fix(vcs): add get default branch for each vcs manager (#5921)

Author: sguiheux

engine/vcs/bitbucketcloud/client_branch.go

@@ -72,6 +72,14 @@ func (client *bitbucketcloudClient) Branches(ctx context.Context, fullname strin
 
 // Branch returns only detail of a branch
 func (client *bitbucketcloudClient) Branch(ctx context.Context, fullname string, filters sdk.VCSBranchFilters) (*sdk.VCSBranch, error) {
+	if filters.Default {
+		repo, err := client.repoByFullname(ctx, fullname)
+		if err != nil {
+			return nil, err
+		}
+		filters.BranchName = repo.Mainbranch.Name
+	}
+
 	repo, err := client.repoByFullname(ctx, fullname)
 	if err != nil {
 		return nil, err

engine/vcs/gerrit/client_branch.go

@@ -46,6 +46,17 @@ func (c *gerritClient) Branches(ctx context.Context, fullname string, _ sdk.VCSB
 
 //Branch retrieves the branch
 func (c *gerritClient) Branch(ctx context.Context, fullname string, filters sdk.VCSBranchFilters) (*sdk.VCSBranch, error) {
+	if filters.Default {
+		bs, err := c.Branches(ctx, fullname, sdk.VCSBranchesFilter{})
+		if err != nil {
+			return nil, err
+		}
+		for _, b := range bs {
+			if b.Default {
+				return &b, nil
+			}
+		}
+	}
 	branch, _, err := c.client.Projects.GetBranch(fullname, filters.BranchName)
 	if err != nil {
 		return nil, sdk.WrapError(err, "unable to get branch")

engine/vcs/gitlab/client_branch.go

@@ -34,6 +34,13 @@ func (c *gitlabClient) Branches(ctx context.Context, fullname string, _ sdk.VCSB
 
 //Branch retrieves the branch
 func (c *gitlabClient) Branch(ctx context.Context, fullname string, filters sdk.VCSBranchFilters) (*sdk.VCSBranch, error) {
+	if filters.Default {
+		p, _, err := c.client.Projects.GetProject(fullname, nil)
+		if err != nil {
+			return nil, err
+		}
+		filters.BranchName = p.DefaultBranch
+	}
 	b, g, err := c.client.Branches.GetBranch(fullname, filters.BranchName)
 	if err != nil {
 		if g != nil && g.StatusCode == 404 {