fix(github): Mergeable requirement for fork PRs (runatlantis#3620)

While using a PR from a fork and the "Github allow mergeable bypass apply" flag, the mergeable checks were run with the wrong owner in the request, leading to 404. By choosing the owner from the head repo data it should work both, for fork PRs and in-repo PRs.

Co-authored-by: Dylan Page <[email protected]>

server/events/vcs/github_client.go

@@ -397,7 +397,7 @@ func isRequiredCheck(check string, required []string) bool {
 // GetCombinedStatusMinusApply checks Statuses for PR, excluding atlantis apply. Returns true if all other statuses are not in failure.
 func (g *GithubClient) GetCombinedStatusMinusApply(repo models.Repo, pull *github.PullRequest, vcstatusname string) (bool, error) {
 	//check combined status api
-	status, _, err := g.client.Repositories.GetCombinedStatus(g.ctx, repo.Owner, repo.Name, *pull.Head.Ref, nil)
+	status, _, err := g.client.Repositories.GetCombinedStatus(g.ctx, *pull.Head.Repo.Owner.Login, repo.Name, *pull.Head.Ref, nil)
 	if err != nil {
 		return false, errors.Wrap(err, "getting combined status")
 	}
@@ -419,7 +419,7 @@ func (g *GithubClient) GetCombinedStatusMinusApply(repo models.Repo, pull *githu
 	}
 
 	//check check suite/check run api
-	checksuites, _, err := g.client.Checks.ListCheckSuitesForRef(context.Background(), repo.Owner, repo.Name, *pull.Head.Ref, nil)
+	checksuites, _, err := g.client.Checks.ListCheckSuitesForRef(context.Background(), *pull.Head.Repo.Owner.Login, repo.Name, *pull.Head.Ref, nil)
 	if err != nil {
 		return false, errors.Wrap(err, "getting check suites for ref")
 	}
@@ -428,7 +428,7 @@ func (g *GithubClient) GetCombinedStatusMinusApply(repo models.Repo, pull *githu
 	for _, c := range checksuites.CheckSuites {
 		if *c.Status == "completed" {
 			//iterate over the runs inside the suite
-			suite, _, err := g.client.Checks.ListCheckRunsCheckSuite(context.Background(), repo.Owner, repo.Name, *c.ID, nil)
+			suite, _, err := g.client.Checks.ListCheckRunsCheckSuite(context.Background(), *pull.Head.Repo.Owner.Login, repo.Name, *c.ID, nil)
 			if err != nil {
 				return false, errors.Wrap(err, "getting check runs for check suite")
 			}

server/events/vcs/github_client_test.go

@@ -692,19 +692,19 @@ func TestGithubClient_PullIsMergeableWithAllowMergeableBypassApply(t *testing.T)
 			testServer := httptest.NewTLSServer(
 				http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 					switch r.RequestURI {
-					case "/api/v3/repos/owner/repo/pulls/1":
+					case "/api/v3/repos/octocat/repo/pulls/1":
 						w.Write([]byte(response)) // nolint: errcheck
 						return
-					case "/api/v3/repos/owner/repo/pulls/1/reviews?per_page=300":
+					case "/api/v3/repos/octocat/repo/pulls/1/reviews?per_page=300":
 						w.Write([]byte("[]")) // nolint: errcheck
 						return
-					case "/api/v3/repos/owner/repo/commits/new-topic/status":
+					case "/api/v3/repos/octocat/repo/commits/new-topic/status":
 						w.Write([]byte(commitJSON)) // nolint: errcheck
 					case "/api/graphql":
 						w.Write([]byte(reviewDecision)) // nolint: errcheck
-					case "/api/v3/repos/owner/repo/branches/main/protection":
+					case "/api/v3/repos/octocat/repo/branches/main/protection":
 						w.Write([]byte(branchProtectionJSON)) // nolint: errcheck
-					case "/api/v3/repos/owner/repo/commits/new-topic/check-suites":
+					case "/api/v3/repos/octocat/repo/commits/new-topic/check-suites":
 						w.Write([]byte(checkSuites)) // nolint: errcheck
 					default:
 						t.Errorf("got unexpected request at %q", r.RequestURI)
@@ -719,8 +719,8 @@ func TestGithubClient_PullIsMergeableWithAllowMergeableBypassApply(t *testing.T)
 			defer disableSSLVerification()()
 
 			actMergeable, err := client.PullIsMergeable(models.Repo{
-				FullName:          "owner/repo",
-				Owner:             "owner",
+				FullName:          "octocat/repo",
+				Owner:             "octocat",
 				Name:              "repo",
 				CloneURL:          "",
 				SanitizedCloneURL: "",