allow `headers` to be a string for fetch()

README.md

@@ -562,13 +562,13 @@ Valid `options` are:
 
   * **id** - < _mixed_ > - _integer_ or _string_ referencing a message part to use when retrieving headers and/or a body. **Default:** (root part/entire message)
 
-  * **headers** - < _mixed_ > - An _array_ of specific headers to retrieve, _boolean_ true to fetch all headers, or an _object_ of the form (**Default:** (no headers)):
+  * **headers** - < _mixed_ > - An _array_ of specific headers to retrieve, a _string_ containing a single header to retrieve, _boolean_ true to fetch all headers, or an _object_ of the form (**Default:** (no headers)):
 
       * **fields** - < _mixed_ > - An _array_ of specific headers to retrieve or _boolean_ true to fetch all headers. **Default:** (all headers)
 
       * **parse** - < _boolean_ > - Parse headers? **Default:** true
 
-  * **headersNot** - < _mixed_ > - An _array_ of specific headers to exclude or an _object_ of the form (**Default:** (no headers)):
+  * **headersNot** - < _mixed_ > - An _array_ of specific headers to exclude, a _string_ containing a single header to exclude, or an _object_ of the form (**Default:** (no headers)):
 
       * **fields** - < _mixed_ > - An _array_ of specific headers to exclude. **Default:** (all headers)
 

lib/imap.js

@@ -995,6 +995,8 @@ ImapConnection.prototype._fetch = function(which, uids, options, what, cb) {
         else {
           if (Array.isArray(wp.headers))
             headers = wp.headers;
+          else if (typeof wp.headers === 'string')
+            headers = [wp.headers];
           else if (typeof wp.headers === 'object') {
             if (wp.headers.fields === undefined)
               wp.headers.fields = true;
@@ -1027,6 +1029,8 @@ ImapConnection.prototype._fetch = function(which, uids, options, what, cb) {
         else {
           if (Array.isArray(wp.headersNot))
             headers = wp.headersNot;
+          else if (typeof wp.headersNot === 'string')
+            headers = [wp.headersNot];
           else if (typeof wp.headersNot === 'object') {
             if (wp.headersNot.fields === undefined)
               wp.headersNot.fields = true;