Update GitHub authorization method

GitHub deprecated the use of query parameter for authentication header. The new way is passing it via HTTP header.

See https://developer.github.com/changes/2020-02-10-deprecating-auth-through-query-param/

Fixes #12

src/github.c

@@ -3,10 +3,8 @@
 #include <jansson.h>
 #include <curl/curl.h>
 
-#define GITHUB_GIST_URL "https://api.github.com/gists?access_token=%s"
-#define ENTERPRISE_GITHUB_GIST_URL "%s/gists?access_token=%s"
-
-#define GITHUB_GIST_URL_ANONYMOUS "https://api.github.com/gists"
+#define GITHUB_GIST_URL "https://api.github.com/gists"
+#define ENTERPRISE_GITHUB_GIST_URL "%s/gists"
 
 #define ENV_ACCESS_TOKEN_KEY "GISTIT_TOKEN"
 #define ENV_GITHUB_API_URL "GISTIT_API_URL"
@@ -15,7 +13,7 @@ struct github_response *github_submit(json_t *content)
 {
 	CURL *curl;
 	CURLcode res;
-	char url[100], userAgent[40], *token, *api_url;
+	char url[100], userAgent[40], authorizationHeader[100], *token, *api_url;
 	struct github_response *response = NULL;
 	struct curl_slist *headers = NULL;
 	long code;
@@ -31,16 +29,18 @@ struct github_response *github_submit(json_t *content)
 		sprintf(userAgent, "User-Agent: %s/%s", PACKAGE_NAME, PACKAGE_VERSION);
 		headers = curl_slist_append(headers, userAgent);
 		api_url = getenv(ENV_GITHUB_API_URL);
+		if (api_url != NULL) {
+			snprintf(url, sizeof(url), ENTERPRISE_GITHUB_GIST_URL, api_url);
+		} else {
+			sprintf(url, GITHUB_GIST_URL);
+		}
+
 		token = getenv(ENV_ACCESS_TOKEN_KEY);
 		if (token != NULL) {
-			if (api_url == NULL) {
-				sprintf(url, GITHUB_GIST_URL, token);
-			} else {
-				sprintf(url, ENTERPRISE_GITHUB_GIST_URL, api_url, token);
-			}
-		} else {
-			sprintf(url, GITHUB_GIST_URL_ANONYMOUS);
+			snprintf(authorizationHeader, sizeof(authorizationHeader), "Authorization: token %s", token);
+			headers = curl_slist_append(headers, authorizationHeader);
 		}
+
 		curl_easy_setopt(curl, CURLOPT_URL, url);
 		curl_easy_setopt(curl, CURLOPT_POST, 1);
 		curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);