Merge pull request #11 from manicminer/support-arbitrary-trunk-rename

support renaming trunk branch in GitLab repo to any arbitrary branch name on the GitHub repo

Author: manicminer

README.md

@@ -38,7 +38,7 @@ Written in Go, this is a cross-platform CLI utility that accepts the following r
   -github-repo string
         the GitHub repository to migrate to
   -github-user string
-        specifies the GitHub user to use, who will author any migrated PRs. can also be sourced from GITHUB_USER environment variable (required)
+        specifies the GitHub user to use, who will author any migrated PRs (required)
   -gitlab-domain string
         specifies the GitLab domain to use (default "gitlab.com")
   -gitlab-project string
@@ -52,8 +52,11 @@ Written in Go, this is a cross-platform CLI utility that accepts the following r
   -projects-csv string
         specifies the path to a CSV file describing projects to migrate (incompatible with -gitlab-project and -github-repo)
   -rename-master-to-main
-        rename master branch to main and update pull requests
-```
+        rename master branch to main and update pull requests (incompatible with -rename-trunk-branch)
+  -rename-trunk-branch string
+        specifies the new trunk branch name (incompatible with -rename-master-to-main)
+  -report
+        report on primitives to be migrated instead of beginning migration```
 
 Use the `-github-user` argument to specify the GitHub username for whom the authentication token was issued (mandatory). You can also specify this with the `GITHUB_USER` environment variable.
 
@@ -75,7 +78,7 @@ Note: If the destination repository does not exist, this tool will attempt to cr
 
 Specify the location of a self-hosted instance of GitLab with the `-gitlab-domain` argument, or a GitHub Enterprise instance with the `-github-domain` argument.
 
-As a bonus, this tool can transparently rename the `master` branch on your GitLab repository, to `main` on the migrated GitHub repository - enable with the `-rename-master-to-main` argument.
+As a bonus, this tool can transparently rename the trunk branch on your GitHub repository - enable with the `-rename-trunk-branch` argument. This will also work for any open merge requests as they are translated to pull requests.
 
 By default, 4 workers will be spawned to migrate up to 4 projects in parallel. You can increase or decrease this with the `-max-concurrency` argument. Note that due to GitHub API rate-limiting, you may not experience any significant speed-up. See [GitHub API docs](https://docs.github.com/en/rest/using-the-rest-api/rate-limits-for-the-rest-api) for details.
 

main.go

@@ -44,7 +44,7 @@ const (
 
 var loop, report bool
 var deleteExistingRepos, enablePullRequests, renameMasterToMain bool
-var githubDomain, githubRepo, githubToken, githubUser, gitlabDomain, gitlabProject, gitlabToken, projectsCsvPath string
+var githubDomain, githubRepo, githubToken, githubUser, gitlabDomain, gitlabProject, gitlabToken, projectsCsvPath, renameTrunkBranch string
 
 var (
 	cache          *objectCache
@@ -150,14 +150,15 @@ func main() {
 
 	flag.BoolVar(&deleteExistingRepos, "delete-existing-repos", false, "whether existing repositories should be deleted before migrating")
 	flag.BoolVar(&enablePullRequests, "migrate-pull-requests", false, "whether pull requests should be migrated")
-	flag.BoolVar(&renameMasterToMain, "rename-master-to-main", false, "rename master branch to main and update pull requests")
+	flag.BoolVar(&renameMasterToMain, "rename-master-to-main", false, "rename master branch to main and update pull requests (incompatible with -rename-trunk-branch)")
 
 	flag.StringVar(&githubDomain, "github-domain", defaultGithubDomain, "specifies the GitHub domain to use")
 	flag.StringVar(&githubRepo, "github-repo", "", "the GitHub repository to migrate to")
 	flag.StringVar(&githubUser, "github-user", "", "specifies the GitHub user to use, who will author any migrated PRs (required)")
 	flag.StringVar(&gitlabDomain, "gitlab-domain", defaultGitlabDomain, "specifies the GitLab domain to use")
 	flag.StringVar(&gitlabProject, "gitlab-project", "", "the GitLab project to migrate")
 	flag.StringVar(&projectsCsvPath, "projects-csv", "", "specifies the path to a CSV file describing projects to migrate (incompatible with -gitlab-project and -github-repo)")
+	flag.StringVar(&renameTrunkBranch, "rename-trunk-branch", "", "specifies the new trunk branch name (incompatible with -rename-master-to-main)")
 
 	flag.IntVar(&maxConcurrency, "max-concurrency", 4, "how many projects to migrate in parallel")
 
@@ -182,6 +183,11 @@ func main() {
 		os.Exit(1)
 	}
 
+	if renameMasterToMain && renameTrunkBranch != "" {
+		logger.Error("cannot specify -rename-master-to-main and -rename-trunk-branch together")
+		os.Exit(1)
+	}
+
 	retryClient := &retryablehttp.Client{
 		HTTPClient:   cleanhttp.DefaultPooledClient(),
 		Logger:       nil,
@@ -584,7 +590,9 @@ func migrateProject(ctx context.Context, proj []string) error {
 	}
 
 	defaultBranch := "main"
-	if !renameMasterToMain && project.DefaultBranch != "" {
+	if renameTrunkBranch != "" {
+		defaultBranch = renameTrunkBranch
+	} else if !renameMasterToMain && project.DefaultBranch != "" {
 		defaultBranch = project.DefaultBranch
 	}
 
@@ -644,19 +652,19 @@ func migrateProject(ctx context.Context, proj []string) error {
 		return fmt.Errorf("cloning gitlab repo: %v", err)
 	}
 
-	if renameMasterToMain {
-		if masterBranch, err := repo.Reference(plumbing.NewBranchReferenceName("master"), false); err == nil {
-			logger.Info("renaming master branch to main prior to push", "name", gitlabPath[1], "group", gitlabPath[0], "sha", masterBranch.Hash())
+	if defaultBranch != project.DefaultBranch {
+		if gitlabTrunk, err := repo.Reference(plumbing.NewBranchReferenceName(project.DefaultBranch), false); err == nil {
+			logger.Info("renaming trunk branch prior to push", "name", gitlabPath[1], "group", gitlabPath[0], "gitlab_trunk", project.DefaultBranch, "github_trunk", defaultBranch, "sha", gitlabTrunk.Hash())
 
-			logger.Debug("creating main branch", "name", gitlabPath[1], "group", gitlabPath[0], "sha", masterBranch.Hash())
-			mainBranch := plumbing.NewHashReference(plumbing.NewBranchReferenceName("main"), masterBranch.Hash())
-			if err = repo.Storer.SetReference(mainBranch); err != nil {
-				return fmt.Errorf("creating main branch: %v", err)
+			logger.Debug("creating new trunk branch", "name", gitlabPath[1], "group", gitlabPath[0], "github_trunk", defaultBranch, "sha", gitlabTrunk.Hash())
+			githubTrunk := plumbing.NewHashReference(plumbing.NewBranchReferenceName(defaultBranch), gitlabTrunk.Hash())
+			if err = repo.Storer.SetReference(githubTrunk); err != nil {
+				return fmt.Errorf("creating trunk branch: %v", err)
 			}
 
-			logger.Debug("deleting master branch", "name", gitlabPath[1], "group", gitlabPath[0], "sha", masterBranch.Hash())
-			if err = repo.Storer.RemoveReference(masterBranch.Name()); err != nil {
-				return fmt.Errorf("deleting master branch: %v", err)
+			logger.Debug("deleting old trunk branch", "name", gitlabPath[1], "group", gitlabPath[0], "gitlab_trunk", project.DefaultBranch, "sha", gitlabTrunk.Hash())
+			if err = repo.Storer.RemoveReference(gitlabTrunk.Name()); err != nil {
+				return fmt.Errorf("deleting old trunk branch: %v", err)
 			}
 		}
 	}
@@ -708,13 +716,13 @@ func migrateProject(ctx context.Context, proj []string) error {
 	}
 
 	if enablePullRequests {
-		migratePullRequests(ctx, githubPath, gitlabPath, project, repo)
+		migratePullRequests(ctx, githubPath, gitlabPath, defaultBranch, project, repo)
 	}
 
 	return nil
 }
 
-func migratePullRequests(ctx context.Context, githubPath, gitlabPath []string, project *gitlab.Project, repo *git.Repository) {
+func migratePullRequests(ctx context.Context, githubPath, gitlabPath []string, defaultBranch string, project *gitlab.Project, repo *git.Repository) {
 	var mergeRequests []*gitlab.MergeRequest
 
 	opts := &gitlab.ListProjectMergeRequestsOptions{
@@ -940,9 +948,9 @@ func migratePullRequests(ctx context.Context, githubPath, gitlabPath []string, p
 			cleanUpBranch = true
 		}
 
-		if renameMasterToMain && mergeRequest.TargetBranch == "master" {
-			logger.Trace("changing target branch from master to main", "name", gitlabPath[1], "group", gitlabPath[0], "project_id", project.ID, "merge_request_id", mergeRequest.IID)
-			mergeRequest.TargetBranch = "main"
+		if defaultBranch != project.DefaultBranch && mergeRequest.TargetBranch == project.DefaultBranch {
+			logger.Trace("changing target trunk branch", "name", gitlabPath[1], "group", gitlabPath[0], "project_id", project.ID, "merge_request_id", mergeRequest.IID, "old_trunk", project.DefaultBranch, "new_trunk", defaultBranch)
+			mergeRequest.TargetBranch = defaultBranch
 		}
 
 		githubAuthorName := mergeRequest.Author.Name