Add gitlab pagination for diff listing

In #1800,
two other places in the code were identified that performed list
requests to gitlab.

This change updates one of those two locations to use pagination.

The other place (acl.go) already had pagination introduced a while ago
in commit 12ba5c5.

Signed-off-by: Ralph Bean <[email protected]>

pkg/provider/gitlab/gitlab.go

@@ -354,25 +354,47 @@ func (v *Provider) GetFiles(_ context.Context, runevent *info.Event) (changedfil
 			"exiting... (hint: did you forget setting a secret on your repo?)")
 	}
 	if runevent.TriggerTarget == triggertype.PullRequest {
-		mrchanges, _, err := v.Client.MergeRequests.ListMergeRequestDiffs(v.targetProjectID, runevent.PullRequestNumber, &gitlab.ListMergeRequestDiffsOptions{})
-		if err != nil {
-			return changedfiles.ChangedFiles{}, err
+		opt := &gitlab.ListMergeRequestDiffsOptions{
+			ListOptions: gitlab.ListOptions{
+				OrderBy:    "id",
+				Pagination: "keyset",
+				PerPage:    20,
+				Sort:       "asc",
+			},
 		}
-
+		options := []gitlab.RequestOptionFunc{}
 		changedFiles := changedfiles.ChangedFiles{}
-		for _, change := range mrchanges {
-			changedFiles.All = append(changedFiles.All, change.NewPath)
-			if change.NewFile {
-				changedFiles.Added = append(changedFiles.Added, change.NewPath)
+
+		for {
+			mrchanges, resp, err := v.Client.MergeRequests.ListMergeRequestDiffs(v.targetProjectID, runevent.PullRequestNumber, opt, options...)
+			if err != nil {
+				return changedfiles.ChangedFiles{}, err
 			}
-			if change.DeletedFile {
-				changedFiles.Deleted = append(changedFiles.Deleted, change.NewPath)
+
+			for _, change := range mrchanges {
+				changedFiles.All = append(changedFiles.All, change.NewPath)
+				if change.NewFile {
+					changedFiles.Added = append(changedFiles.Added, change.NewPath)
+				}
+				if change.DeletedFile {
+					changedFiles.Deleted = append(changedFiles.Deleted, change.NewPath)
+				}
+				if !change.RenamedFile && !change.DeletedFile && !change.NewFile {
+					changedFiles.Modified = append(changedFiles.Modified, change.NewPath)
+				}
+				if change.RenamedFile {
+					changedFiles.Renamed = append(changedFiles.Renamed, change.NewPath)
+				}
 			}
-			if !change.RenamedFile && !change.DeletedFile && !change.NewFile {
-				changedFiles.Modified = append(changedFiles.Modified, change.NewPath)
+
+			// Exit the loop when we've seen all pages.
+			if resp.NextLink == "" {
+				break
 			}
-			if change.RenamedFile {
-				changedFiles.Renamed = append(changedFiles.Renamed, change.NewPath)
+
+			// Otherwise, set param to query the next page
+			options = []gitlab.RequestOptionFunc{
+				gitlab.WithKeysetPaginationParameters(resp.NextLink),
 			}
 		}
 		return changedFiles, nil