gitlab: Fix 'mr list' limits

The command 'lab mr list --author $author_name --state merged' was
returning a list of 100 for each engineer on a project.  Evidence in the
git tree showed that this was not the case (most had more than 100).

This was due to a calcluational error in the MRList() code.  Implement a
new algorithm that correctly returns all MRs instead of the last 100.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>

Author: prarit

internal/gitlab/gitlab.go

@@ -433,19 +433,26 @@ func MRGet(projID interface{}, id int) (*gitlab.MergeRequest, error) {
 
 // MRList lists the MRs on a GitLab project
 func MRList(projID interface{}, opts gitlab.ListProjectMergeRequestsOptions, n int) ([]*gitlab.MergeRequest, error) {
-	if n == -1 {
-		n = maxItemsPerPage
-	}
-
 	var list []*gitlab.MergeRequest
-	for len(list) < n {
-		opts.PerPage = n - len(list)
+	for true {
+		opts.PerPage = maxItemsPerPage
+		if n != -1 {
+			opts.PerPage = n - len(list)
+			if opts.PerPage > maxItemsPerPage {
+				opts.PerPage = maxItemsPerPage
+			}
+		}
+
 		mrs, resp, err := lab.MergeRequests.ListProjectMergeRequests(projID, &opts)
 		if err != nil {
 			return nil, err
 		}
 		list = append(list, mrs...)
 
+		if len(list) == n {
+			break
+		}
+
 		var ok bool
 		if opts.Page, ok = hasNextPage(resp); !ok {
 			break