Close #26: Filter PRs by updated date instead of commit date

This supersedes #205.

This resource can inadvertently miss Pull Requests due to out-of-order
commits across PRs. If PR#2 is opened after PR#1, but the head commit
of PR#2 is older than the head commit of PR#1, the resource will not
include PR#2 in the list of new versions provided to Concourse.

In #205, I removed the date filter entirely.  This ensures that the PR
resource will find all PRs that match the explicitly-configured filters.
While Concourse can detect and ignore duplicate versions, it has to run
a database query for every version returned by a `check`, so removing
the date filter entirely would increase load on a Concourse database.
(That said, I'm not sure whether this increased load is a particular
concern, and other resources don't seem to make much effort to avoid
returning duplicate versions from a `check`.)

To avoid that extra load on a Concourse database, this change instead
replaces the filter by commit date in `check.go` with a filter by updated
date in the GraphQL query to list pull requests.  This should reduce the
number of duplicate versions returned by a `check` while still allowing
the PR resource to detect PRs with out-of-order head commits.

check.go

@@ -20,7 +20,7 @@ func Check(request CheckRequest, manager Github) (CheckResponse, error) {
 		filterStates = request.Source.States
 	}
 
-	pulls, err := manager.ListPullRequests(filterStates)
+	pulls, err := manager.ListPullRequests(filterStates, request.Version.CommittedDate)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get last commits: %s", err)
 	}
@@ -44,11 +44,6 @@ Loop:
 			continue
 		}
 
-		// Filter out commits that are too old.
-		if !p.UpdatedDate().Time.After(request.Version.CommittedDate) {
-			continue
-		}
-
 		// Filter out pull request if it does not contain at least one of the desired labels
 		if len(request.Source.Labels) > 0 {
 			labelFound := false

check_test.go

@@ -50,7 +50,7 @@ func TestCheck(t *testing.T) {
 		},
 
 		{
-			description: "check returns the previous version when its still latest",
+			description: "check returns all open PRs if there is a previous",
 			source: resource.Source{
 				Repository:  "itsdalmo/test-repository",
 				AccessToken: "oauthtoken",
@@ -59,20 +59,13 @@ func TestCheck(t *testing.T) {
 			pullRequests: testPullRequests,
 			files:        [][]string{},
 			expected: resource.CheckResponse{
-				resource.NewVersion(testPullRequests[1]),
-			},
-		},
-
-		{
-			description: "check returns all new versions since the last",
-			source: resource.Source{
-				Repository:  "itsdalmo/test-repository",
-				AccessToken: "oauthtoken",
-			},
-			version:      resource.NewVersion(testPullRequests[3]),
-			pullRequests: testPullRequests,
-			files:        [][]string{},
-			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[11]),
+				resource.NewVersion(testPullRequests[8]),
+				resource.NewVersion(testPullRequests[7]),
+				resource.NewVersion(testPullRequests[6]),
+				resource.NewVersion(testPullRequests[5]),
+				resource.NewVersion(testPullRequests[4]),
+				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[2]),
 				resource.NewVersion(testPullRequests[1]),
 			},
@@ -93,6 +86,7 @@ func TestCheck(t *testing.T) {
 				{"terraform/modules/variables.tf", "travis.yml"},
 			},
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[2]),
 			},
 		},
@@ -112,6 +106,7 @@ func TestCheck(t *testing.T) {
 				{"terraform/modules/variables.tf", "travis.yml"},
 			},
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[2]),
 			},
 		},
@@ -126,6 +121,15 @@ func TestCheck(t *testing.T) {
 			version:      resource.NewVersion(testPullRequests[1]),
 			pullRequests: testPullRequests,
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[11]),
+				resource.NewVersion(testPullRequests[8]),
+				resource.NewVersion(testPullRequests[7]),
+				resource.NewVersion(testPullRequests[6]),
+				resource.NewVersion(testPullRequests[5]),
+				resource.NewVersion(testPullRequests[4]),
+				resource.NewVersion(testPullRequests[3]),
+				resource.NewVersion(testPullRequests[2]),
+				resource.NewVersion(testPullRequests[1]),
 				resource.NewVersion(testPullRequests[0]),
 			},
 		},
@@ -140,6 +144,13 @@ func TestCheck(t *testing.T) {
 			version:      resource.NewVersion(testPullRequests[3]),
 			pullRequests: testPullRequests,
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[11]),
+				resource.NewVersion(testPullRequests[8]),
+				resource.NewVersion(testPullRequests[7]),
+				resource.NewVersion(testPullRequests[6]),
+				resource.NewVersion(testPullRequests[5]),
+				resource.NewVersion(testPullRequests[4]),
+				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[1]),
 			},
 		},
@@ -154,6 +165,13 @@ func TestCheck(t *testing.T) {
 			version:      resource.NewVersion(testPullRequests[3]),
 			pullRequests: testPullRequests,
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[11]),
+				resource.NewVersion(testPullRequests[8]),
+				resource.NewVersion(testPullRequests[7]),
+				resource.NewVersion(testPullRequests[6]),
+				resource.NewVersion(testPullRequests[5]),
+				resource.NewVersion(testPullRequests[4]),
+				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[2]),
 				resource.NewVersion(testPullRequests[1]),
 			},
@@ -169,6 +187,11 @@ func TestCheck(t *testing.T) {
 			version:      resource.NewVersion(testPullRequests[5]),
 			pullRequests: testPullRequests,
 			expected: resource.CheckResponse{
+				resource.NewVersion(testPullRequests[11]),
+				resource.NewVersion(testPullRequests[8]),
+				resource.NewVersion(testPullRequests[7]),
+				resource.NewVersion(testPullRequests[6]),
+				resource.NewVersion(testPullRequests[5]),
 				resource.NewVersion(testPullRequests[3]),
 				resource.NewVersion(testPullRequests[2]),
 				resource.NewVersion(testPullRequests[1]),