Add support for placeholder merge requests

Author: mschoettle

README.md

@@ -206,8 +206,18 @@ Set to `true` (default) to enable using the [GitHub preview API for importing is
 
 ### usePlaceholderIssuesForMissingIssues
 
+NOTE: This setting requires `usePlaceholderIssuesForMissingMergeRequests` to be set to `false` (default).
+
 If this is set to `true` (default) then the migration process will automatically create empty dummy issues for every 'missing' GitLab issue (if you deleted a GitLab issue for example). Those issues will be closed on Github and they ensure that the issue ids stay the same on both GitLab and Github.
 
+### usePlaceholderIssuesForMissingMergeRequests
+
+NOTE: GitLab has distinct numbers for issues and merge requests whereas GitHub treats pull requests as issues.
+Only use this setting if your GitLab repository does not have issues or you do not intend on migrating them.
+This setting therefore requires `usePlaceholderIssuesForMissingIssues` to be set to `false`.
+
+If this is set to `true` then the migration process will automatically create empty dummy issues for every 'missing' GitLab merge request (if you deleted a GitLab merge request for example). Those issues will be closed on Github and they ensure that the issue ids stay the same on both GitLab and Github.
+
 #### usePlaceholderMilestonesForMissingMilestones
 
 If this is set to `true` (default) then the migration process will automatically create empty dummy milestones for every 'missing' GitLab milestone (if you deleted a GitLab milestone for example). Those milestones will be closed on Github and they ensure that the milestone ids stay the same on both GitLab and Github.

src/githubHelper.ts

@@ -900,6 +900,15 @@ export class GithubHelper {
   async createPullRequestAndComments(
     mergeRequest: GitLabMergeRequest
   ): Promise<void> {
+    // Use the issue creation for placeholder issues
+    if (mergeRequest.isPlaceholder) {
+      let issue = mergeRequest as unknown;
+      await this.createIssueAndComments(issue as GitLabIssue);
+      console.log(`Created placeholder issue for placeholder merge request #${mergeRequest.iid}`);
+
+      return;
+    }
+
     let pullRequestData = await this.createPullRequest(mergeRequest);
 
     // createPullRequest() returns an issue number if a PR could not be created and

src/settings.ts

@@ -24,6 +24,7 @@ export default interface Settings {
   useIssueImportAPI: boolean;
   usePlaceholderMilestonesForMissingMilestones: boolean;
   usePlaceholderIssuesForMissingIssues: boolean;
+  usePlaceholderIssuesForMissingMergeRequests: boolean;
   useReplacementIssuesForCreationFails: boolean;
   useIssuesForAllMergeRequests: boolean;
   filterByLabel?: string;