upload: add -R/--replace switch

A PATCH would've been better in order to make the whole shebang atomic and
save some code. However, the Github API documentation seems to imply that
you can only use PATCH to edit metadata:
https://developer.github.com/v3/repos/releases/#edit-a-release-asset.

Fixes github-release#38.
Fixes github-release#39.

assets.go

@@ -19,3 +19,14 @@ type Asset struct {
 	Created     time.Time `json:"created_at"`
 	Published   time.Time `json:"published_at"`
 }
+
+// findAssetID returns the asset ID if name can be found in assets,
+// otherwise returns -1.
+func findAssetID(assets []Asset, name string) int {
+	for _, asset := range assets {
+		if asset.Name == name {
+			return asset.Id
+		}
+	}
+	return -1
+}

cmd.go

@@ -94,6 +94,17 @@ func uploadcmd(opt Options) error {
 		return err
 	}
 
+	// If asked to replace, first delete the existing asset, if any.
+	if assetID := findAssetID(rel.Assets, name); opt.Upload.Replace && assetID != -1 {
+		URL := nvls(EnvApiEndpoint, github.DefaultBaseURL) +
+			fmt.Sprintf(ASSET_DOWNLOAD_URI, user, repo, assetID)
+		resp, err := github.DoAuthRequest("DELETE", URL, "application/json", token, nil, nil)
+		if err != nil || resp.StatusCode != http.StatusNoContent {
+			return fmt.Errorf("could not replace asset %s (ID: %d), deletion failed (error: %v, status: %s)",
+				name, assetID, err, resp.Status)
+		}
+	}
+
 	v := url.Values{}
 	v.Set("name", name)
 	if label != "" {
@@ -154,14 +165,8 @@ func downloadcmd(opt Options) error {
 		return err
 	}
 
-	assetId := 0
-	for _, asset := range rel.Assets {
-		if asset.Name == name {
-			assetId = asset.Id
-		}
-	}
-
-	if assetId == 0 {
+	assetID := findAssetID(rel.Assets, name)
+	if assetID == -1 {
 		return fmt.Errorf("coud not find asset named %s", name)
 	}
 
@@ -170,7 +175,7 @@ func downloadcmd(opt Options) error {
 		// Use the regular github.com site it we don't have a token.
 		resp, err = http.Get("https://github.com" + fmt.Sprintf("/%s/%s/releases/download/%s/%s", user, repo, tag, name))
 	} else {
-		url := nvls(EnvApiEndpoint, github.DefaultBaseURL) + fmt.Sprintf(ASSET_DOWNLOAD_URI, user, repo, assetId)
+		url := nvls(EnvApiEndpoint, github.DefaultBaseURL) + fmt.Sprintf(ASSET_DOWNLOAD_URI, user, repo, assetID)
 		resp, err = github.DoAuthRequest("GET", url, "", token, map[string]string{
 			"Accept": "application/octet-stream",
 		}, nil)
@@ -401,7 +406,7 @@ func deletecmd(opt Options) error {
 	resp, err := github.DoAuthRequest("DELETE", baseURL+fmt.Sprintf("/repos/%s/%s/releases/%d",
 		user, repo, id), "application/json", token, nil, nil)
 	if err != nil {
-		return fmt.Errorf("release deletion unsuccesful, %v", err)
+		return fmt.Errorf("release deletion failed: %v", err)
 	}
 	defer resp.Body.Close()
 

github-release.go

@@ -26,13 +26,14 @@ type Options struct {
 		Name   string `goptions:"-n, --name, description='Name of the file', obligatory"`
 	} `goptions:"download"`
 	Upload struct {
-		Token string   `goptions:"-s, --security-token, description='Github token (required if $GITHUB_TOKEN not set)'"`
-		User  string   `goptions:"-u, --user, description='Github repo user or organisation (required if $GITHUB_USER not set)'"`
-		Repo  string   `goptions:"-r, --repo, description='Github repo (required if $GITHUB_REPO not set)'"`
-		Tag   string   `goptions:"-t, --tag, description='Git tag to upload to', obligatory"`
-		Name  string   `goptions:"-n, --name, description='Name of the file', obligatory"`
-		Label string   `goptions:"-l, --label, description='Label (description) of the file'"`
-		File  *os.File `goptions:"-f, --file, description='File to upload (use - for stdin)', rdonly, obligatory"`
+		Token   string   `goptions:"-s, --security-token, description='Github token (required if $GITHUB_TOKEN not set)'"`
+		User    string   `goptions:"-u, --user, description='Github repo user or organisation (required if $GITHUB_USER not set)'"`
+		Repo    string   `goptions:"-r, --repo, description='Github repo (required if $GITHUB_REPO not set)'"`
+		Tag     string   `goptions:"-t, --tag, description='Git tag to upload to', obligatory"`
+		Name    string   `goptions:"-n, --name, description='Name of the file', obligatory"`
+		Label   string   `goptions:"-l, --label, description='Label (description) of the file'"`
+		File    *os.File `goptions:"-f, --file, description='File to upload (use - for stdin)', rdonly, obligatory"`
+		Replace bool     `goptions:"-R, --replace, description='Replace asset with same name if it already exists (WARNING: not atomic, failure to upload will remove the original asset too)'"`
 	} `goptions:"upload"`
 	Release struct {
 		Token      string `goptions:"-s, --security-token, description='Github token (required if $GITHUB_TOKEN not set)'"`