Don't ask for git credentials in non-interactive session

This is done by setting GIT_TERMINAL_PROMPT variable

- fixes #956
- fixes #1009

lib/core/resolvers/GitResolver.js

@@ -27,6 +27,7 @@ function GitResolver(decEndpoint, config, logger) {
     mkdirp.sync(config.storage.empty);
     process.env.GIT_TEMPLATE_DIR = config.storage.empty;
     process.env.GIT_SSL_NO_VERIFY = (!config.strictSsl).toString();
+    process.env.GIT_TERMINAL_PROMPT = config.interactive ? '1' : '0';
 
     Resolver.call(this, decEndpoint, config, logger);