Ensure to generate file creation URL (#635)

**What this PR does / why we need it**:
Each deployment config template comes with a file creation URL, which is for creating a new file under the git path, with template content as default value. Something like:
https://github.com/pipe-cd/debug/new/master/kubernetes/analysis-by-metrics?filename=.pipe.yaml&value=%23+This+configures+a+non-progressive+delivery.%0AapiVersion%3A+pipecd.dev%2Fv1beta1%0Akind%3A+KubernetesApp%0Aspec%3A%0A++input%3A%0A++++manifests%3A%0A++++++-+deployment.yaml%0A++++++-+service.yaml%0A++++kubectlVersion%3A+2.1.1

Whereas, I'm getting an issue about specifying filename: isaacs/github#1527. I'll be glad to address it later.

**Which issue(s) this PR fixes**:

Fixes #627

**Does this PR introduce a user-facing change?**:
<!--
If no, just write "NONE" in the release-note block below.
-->
```release-note
NONE
```

This PR was merged by Kapetanios.

pkg/app/api/api/web_api.go

@@ -818,8 +818,13 @@ func (a *WebAPI) GetCommand(ctx context.Context, req *webservice.GetCommandReque
 }
 
 func (a *WebAPI) ListDeploymentConfigTemplates(ctx context.Context, req *webservice.ListDeploymentConfigTemplatesRequest) (*webservice.ListDeploymentConfigTemplatesResponse, error) {
+	app, err := a.getApplication(ctx, req.ApplicationId)
+	if err != nil {
+		return nil, err
+	}
+
 	var templates []*webservice.DeploymentConfigTemplate
-	switch req.ApplicationKind {
+	switch app.Kind {
 	case model.ApplicationKind_KUBERNETES:
 		templates = k8sDeploymentConfigTemplates
 	case model.ApplicationKind_TERRAFORM:
@@ -831,7 +836,19 @@ func (a *WebAPI) ListDeploymentConfigTemplates(ctx context.Context, req *webserv
 	case model.ApplicationKind_CLOUDRUN:
 		templates = cloudrunDeploymentConfigTemplates
 	default:
-		return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("unknown application kind %v", req.ApplicationKind))
+		return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("unknown application kind %v", app.Kind))
+	}
+	for _, t := range templates {
+		g := app.GetGitPath()
+		filename := g.ConfigFilename
+		if filename == "" {
+			filename = ".pipe.yaml"
+		}
+		t.FileCreationUrl, err = git.MakeFileCreationURL(g.Repo.Remote, g.Path, g.Repo.Branch, filename, t.Content)
+		if err != nil {
+			a.logger.Error("failed to make a link to creat a file", zap.Error(err))
+			return nil, status.Error(codes.Internal, "failed to make a link to creat a file")
+		}
 	}
 
 	if len(req.Labels) == 0 {

pkg/app/api/service/webservice/service.proto

@@ -164,6 +164,7 @@ message AddApplicationRequest {
 }
 
 message AddApplicationResponse {
+    string application_id = 1 [(validate.rules).string.min_len = 1];
 }
 
 message EnableApplicationRequest {
@@ -331,6 +332,8 @@ message DeploymentConfigTemplate {
     string name = 2 [(validate.rules).string.min_len = 1];
     repeated DeploymentConfigTemplateLabel labels = 3;
     string content = 4 [(validate.rules).string.min_len = 1];
+    // An HTML link to create a new file under the git path, with template content as default value.
+    string file_creation_url = 5;
 }
 
 enum DeploymentConfigTemplateLabel {
@@ -339,7 +342,7 @@ enum DeploymentConfigTemplateLabel {
 }
 
 message ListDeploymentConfigTemplatesRequest {
-    pipe.model.ApplicationKind application_kind = 1 [(validate.rules).enum.defined_only = true];
+    string application_id = 1 [(validate.rules).string.min_len = 1];
     repeated DeploymentConfigTemplateLabel labels = 2;
 }
 

pkg/git/url.go

@@ -86,6 +86,42 @@ func MakeDirURL(repoURL, dir, branch string) (string, error) {
 	return fmt.Sprintf("%s://%s/%s/%s/%s/%s", scheme, u.Host, repoPath, subPath, branch, dir), nil
 }
 
+// MakeFileCreationURL builds a link to create a file under the given directory.
+func MakeFileCreationURL(repoURL, dir, branch, filename, value string) (string, error) {
+	if branch == "" {
+		return "", fmt.Errorf("no branch given")
+	}
+	u, err := parseGitURL(repoURL)
+	if err != nil {
+		return "", err
+	}
+
+	if u.Scheme == "ssh" {
+		u.Scheme = "https"
+		u.User = nil
+	}
+	repoPath := strings.TrimSuffix(strings.Trim(u.Path, "/"), ".git")
+	dir = strings.Trim(dir, "/")
+
+	switch u.Host {
+	case "github.com":
+		u.Path = fmt.Sprintf("%s/%s/%s/%s", repoPath, "new", branch, dir)
+		params := &url.Values{}
+		if filename != "" {
+			params.Add("filename", filename)
+		}
+		if value != "" {
+			params.Add("value", value)
+		}
+		u.RawQuery = params.Encode()
+	default:
+		// TODO: Allow users to specify git host
+		u.Path = fmt.Sprintf("%s/%s/%s/%s", repoPath, "new", branch, dir)
+	}
+
+	return u.String(), nil
+}
+
 var (
 	knownSchemes = map[string]interface{}{
 		"ssh":     struct{}{},

pkg/git/url_test.go

@@ -163,6 +163,75 @@ func TestMakeDirURL(t *testing.T) {
 		})
 	}
 }
+
+func TestMakeFileCreationURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		repoURL  string
+		dir      string
+		branch   string
+		filename string
+		value    string
+		want     string
+		wantErr  bool
+	}{
+		{
+			name:     "given filename",
+			repoURL:  "git@github.com:org/repo.git",
+			dir:      "path/to",
+			branch:   "abc",
+			filename: "foo.txt",
+			want:     "https://github.com/org/repo/new/abc/path/to?filename=foo.txt",
+			wantErr:  false,
+		},
+		{
+			name:     "given filename and value",
+			repoURL:  "git@github.com:org/repo.git",
+			dir:      "path/to",
+			branch:   "abc",
+			filename: "foo.txt",
+			value: `# Comment
+foo:
+  bar:
+    baz:
+      - a
+      - b
+`,
+			want:    "https://github.com/org/repo/new/abc/path/to?filename=foo.txt&value=%23+Comment%0Afoo%3A%0A++bar%3A%0A++++baz%3A%0A++++++-+a%0A++++++-+b%0A",
+			wantErr: false,
+		},
+		{
+			name:    "ssh to unsupported git host",
+			repoURL: "git@foo.com:org/repo.git",
+			dir:     "path/to",
+			branch:  "abc",
+			want:    "https://foo.com/org/repo/new/abc/path/to",
+			wantErr: false,
+		},
+		{
+			name:    "no branch given",
+			repoURL: "1234abcd",
+			dir:     "path/to",
+			wantErr: true,
+		},
+		{
+			name:    "unparseable url",
+			repoURL: "1234abcd",
+			dir:     "path/to",
+			branch:  "abc",
+			want:    "",
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := MakeFileCreationURL(tt.repoURL, tt.dir, tt.branch, tt.filename, tt.value)
+			assert.Equal(t, tt.wantErr, err != nil)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
+
 func TestParseGitURL(t *testing.T) {
 	tests := []struct {
 		name    string