Merge pull request #20 from manicminer/feature/trim-github-branches

Optionally trim branches on GitHub that are not present in GitLab

Author: manicminer

README.md

@@ -61,6 +61,8 @@ Written in Go, this is a cross-platform CLI utility that accepts the following r
         report on primitives to be migrated instead of beginning migration
   -skip-invalid-merge-requests
         when true, will log and skip invalid merge requests instead of raising an error
+  -trim-branches-on-github
+        when true, will delete any branches on GitHub that are no longer present in GitLab
   -version
         output version information
 ```

cache.go

@@ -8,7 +8,8 @@ import (
 )
 
 const (
-	githubPullRequestCacheType uint8 = iota
+	githubBranchesCacheType uint8 = iota
+	githubPullRequestCacheType
 	githubSearchResultsCacheType
 	githubUserCacheType
 	gitlabUserCacheType
@@ -21,6 +22,7 @@ type objectCache struct {
 
 func newObjectCache() *objectCache {
 	store := make(map[uint8]map[string]any)
+	store[githubBranchesCacheType] = make(map[string]any)
 	store[githubPullRequestCacheType] = make(map[string]any)
 	store[githubSearchResultsCacheType] = make(map[string]any)
 	store[githubUserCacheType] = make(map[string]any)
@@ -32,6 +34,21 @@ func newObjectCache() *objectCache {
 	}
 }
 
+func (c objectCache) getGithubBranches(query string) []*github.Branch {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
+	if v, ok := c.store[githubBranchesCacheType][query]; ok {
+		return v.([]*github.Branch)
+	}
+	return nil
+}
+
+func (c objectCache) setGithubBranches(query string, result []*github.Branch) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	c.store[githubBranchesCacheType][query] = result
+}
+
 func (c objectCache) getGithubPullRequest(query string) *github.PullRequest {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()

helper.go

@@ -14,6 +14,28 @@ import (
 	"github.com/xanzy/go-gitlab"
 )
 
+func getGithubBranches(ctx context.Context, owner, repo string) ([]*github.Branch, error) {
+	var err error
+	cacheToken := fmt.Sprintf("%s/%s", owner, repo)
+	result := cache.getGithubBranches(cacheToken)
+	if result == nil {
+		logger.Debug("listing branches")
+		result, _, err = gh.Repositories.ListBranches(ctx, owner, repo, nil)
+		if err != nil {
+			return nil, fmt.Errorf("listing branches: %v", err)
+		}
+
+		if result == nil {
+			return nil, fmt.Errorf("nil result was returned when listing branches for repo: %s/%s", owner, repo)
+		}
+
+		logger.Trace("caching GitHub branches", "repo", fmt.Sprintf("%s/%s", owner, repo))
+		cache.setGithubBranches(cacheToken, result)
+	}
+
+	return result, nil
+}
+
 func getGithubPullRequest(ctx context.Context, org, repo string, prNumber int) (*github.PullRequest, error) {
 	var err error
 	cacheToken := fmt.Sprintf("%s/%s/%d", org, repo, prNumber)

main.go

@@ -30,7 +30,7 @@ const (
 )
 
 var loop, report bool
-var deleteExistingRepos, enablePullRequests, renameMasterToMain, skipInvalidMergeRequests bool
+var deleteExistingRepos, enablePullRequests, renameMasterToMain, skipInvalidMergeRequests, trimGithubBranches bool
 var githubDomain, githubRepo, githubToken, githubUser, gitlabDomain, gitlabProject, gitlabToken, projectsCsvPath, renameTrunkBranch string
 var mergeRequestsAge int
 
@@ -98,6 +98,7 @@ func main() {
 	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 (incompatible with -rename-trunk-branch)")
 	flag.BoolVar(&skipInvalidMergeRequests, "skip-invalid-merge-requests", false, "when true, will log and skip invalid merge requests instead of raising an error")
+	flag.BoolVar(&trimGithubBranches, "trim-branches-on-github", false, "when true, will delete any branches on GitHub that are no longer present in GitLab")
 	flag.BoolVar(&showVersion, "version", false, "output version information")
 
 	flag.StringVar(&githubDomain, "github-domain", defaultGithubDomain, "specifies the GitHub domain to use")

project.go

@@ -185,8 +185,10 @@ func (p *project) migrate(ctx context.Context) error {
 		return fmt.Errorf("retrieving branches: %v", err)
 	}
 
+	gitlabBranches := make([]string, 0)
 	refSpecs := make([]config.RefSpec, 0)
 	if err = branches.ForEach(func(ref *plumbing.Reference) error {
+		gitlabBranches = append(gitlabBranches, ref.Name().Short())
 		refSpecs = append(refSpecs, config.RefSpec(fmt.Sprintf("%[1]s:%[1]s", ref.Name())))
 		return nil
 	}); err != nil {
@@ -207,6 +209,41 @@ func (p *project) migrate(ctx context.Context) error {
 		}
 	}
 
+	if trimGithubBranches {
+		logger.Debug("determining old branches to trim on GitHub repository", "name", p.gitlabPath[1], "group", p.gitlabPath[0], "url", githubUrl)
+		refSpecsToDelete := make([]config.RefSpec, 0)
+		githubBranches, err := getGithubBranches(ctx, p.githubPath[0], p.githubPath[1])
+		if err != nil {
+			return fmt.Errorf("listing branches from GitHub: %v", err)
+		}
+		for _, githubBranch := range githubBranches {
+			found := false
+			for _, gitlabBranch := range gitlabBranches {
+				if githubBranch.Name != nil && *githubBranch.Name == gitlabBranch {
+					found = true
+					break
+				}
+			}
+			if !found {
+				refSpecsToDelete = append(refSpecsToDelete, config.RefSpec(fmt.Sprintf(":refs/heads/%s", *githubBranch.Name)))
+			}
+		}
+
+		logger.Debug("trimming old branches on GitHub repository", "name", p.gitlabPath[1], "group", p.gitlabPath[0], "url", githubUrl, "count", len(refSpecs))
+		if err = p.repo.PushContext(ctx, &git.PushOptions{
+			RemoteName: "github",
+			Force:      true,
+			RefSpecs:   refSpecsToDelete,
+			//Prune:      true, // causes error, attempts to delete main branch
+		}); err != nil {
+			if errors.Is(err, git.NoErrAlreadyUpToDate) {
+				logger.Debug("repository already up-to-date on GitHub", "name", p.gitlabPath[1], "group", p.gitlabPath[0], "url", githubUrl)
+			} else {
+				return fmt.Errorf("pushing to github repo: %v", err)
+			}
+		}
+	}
+
 	logger.Debug("force-pushing tags to GitHub repository", "name", p.gitlabPath[1], "group", p.gitlabPath[0], "url", githubUrl)
 	if err = p.repo.PushContext(ctx, &git.PushOptions{
 		RemoteName: "github",