tk tool importers: Follow through main files (grafana#888)

If a main file imports another main file, we currently don't follow
This can lead to Tanka not diffing/applying all the environments it should, when the base environment changes

pkg/jsonnet/find_importers.go

@@ -266,9 +266,8 @@ func findImporters(root string, searchForFile string, chain map[string]struct{})
 			if isImporter {
 				if jsonnetFileContent.IsMainFile {
 					importers = append(importers, jsonnetFilePath)
-				} else {
-					intermediateImporters = append(intermediateImporters, jsonnetFilePath)
 				}
+				intermediateImporters = append(intermediateImporters, jsonnetFilePath)
 				break
 			}
 		}

pkg/jsonnet/find_importers_test.go

@@ -197,6 +197,16 @@ func findImportersTestCases(t testing.TB) []findImportersTestCase {
 				absPath(t, "testdata/findImporters/environments/no-imports/main.jsonnet"),
 			},
 		},
+		{
+			name: "imports through a main file are followed",
+			files: []string{
+				"testdata/findImporters/environments/import-other-main-file/env2/file.libsonnet",
+			},
+			expectedImporters: []string{
+				absPath(t, "testdata/findImporters/environments/import-other-main-file/env1/main.jsonnet"),
+				absPath(t, "testdata/findImporters/environments/import-other-main-file/env2/main.jsonnet"),
+			},
+		},
 	}
 }
 

pkg/jsonnet/testdata/findImporters/environments/import-other-main-file/env1/main.jsonnet

@@ -0,0 +1,3 @@
+{
+  otherMain: import '../env2/main.jsonnet',
+}

pkg/jsonnet/testdata/findImporters/environments/import-other-main-file/env2/file.libsonnet

@@ -0,0 +1 @@
+{}

pkg/jsonnet/testdata/findImporters/environments/import-other-main-file/env2/main.jsonnet

@@ -0,0 +1,3 @@
+{
+  myfile: import 'file.libsonnet',
+}