Docs: Replace #NUMBER Trac issue references with trac-NUMBER

The GitHub UI treats `#NUMBER` as referring to its own issues which is confusing
when in jQuery source it's usually referring to the old deprecated Trac instance
at https://bugs.jquery.com. This change replaces all such Trac references with
`trac-NUMBER`.

A few of the references came with the Sizzle integration and referred to the
Sizzle GitHub bug tracker. Those have been replaced with full links instead.

A new entry describing issue reference conventions has been added to README.

Closes gh-4993

Author: mgol

README.md

@@ -14,6 +14,12 @@ In the spirit of open source software development, jQuery always encourages comm
 2. [Core Style Guide](https://contribute.jquery.org/style-guide/js/)
 3. [Writing Code for jQuery Foundation Projects](https://contribute.jquery.org/code/)
 
+### References to issues/PRs
+
+GitHub issues/PRs are usually referenced via `gh-NUMBER`, where `NUMBER` is the numerical ID of the issue/PR. You can find such an issue/PR under `https://github.com/jquery/jquery/issues/NUMBER`.
+
+jQuery has used a different bug tracker - based on Trac - in the past, available under [bugs.jquery.com](https://bugs.jquery.com/). It is being kept in read only mode so that referring to past discussions is possible. When jQuery source references one of those issues, it uses the pattern `trac-NUMBER`, where `NUMBER` is the numerical ID of the issue. You can find such an issue under `https://bugs.jquery.com/ticket/NUMBER`.
+
 
 Environments in which to use jQuery
 --------------------------------------

src/ajax.js

@@ -17,7 +17,7 @@ var
 	rantiCache = /([?&])_=[^&]*/,
 	rheaders = /^(.*?):[ \t]*([^\r\n]*)$/mg,
 
-	// #7653, #8125, #8152: local protocol detection
+	// trac-7653, trac-8125, trac-8152: local protocol detection
 	rlocalProtocol = /^(?:about|app|app-storage|.+-extension|file|res|widget):$/,
 	rnoContent = /^(?:GET|HEAD)$/,
 	rprotocol = /^\/\//,
@@ -40,7 +40,7 @@ var
 	 */
 	transports = {},
 
-	// Avoid comment-prolog char sequence (#10098); must appease lint and evade compression
+	// Avoid comment-prolog char sequence (trac-10098); must appease lint and evade compression
 	allTypes = "*/".concat( "*" ),
 
 	// Anchor tag for parsing the document origin
@@ -111,7 +111,7 @@ function inspectPrefiltersOrTransports( structure, options, originalOptions, jqX
 
 // A special extend for ajax options
 // that takes "flat" options (not to be deep extended)
-// Fixes #9887
+// Fixes trac-9887
 function ajaxExtend( target, src ) {
 	var key, deep,
 		flatOptions = jQuery.ajaxSettings.flatOptions || {};
@@ -528,12 +528,12 @@ jQuery.extend( {
 		deferred.promise( jqXHR );
 
 		// Add protocol if not provided (prefilters might expect it)
-		// Handle falsy url in the settings object (#10093: consistency with old signature)
+		// Handle falsy url in the settings object (trac-10093: consistency with old signature)
 		// We also use the url parameter if available
 		s.url = ( ( url || s.url || location.href ) + "" )
 			.replace( rprotocol, location.protocol + "//" );
 
-		// Alias method option to type as per ticket #12004
+		// Alias method option to type as per ticket trac-12004
 		s.type = options.method || options.type || s.method || s.type;
 
 		// Extract dataTypes list
@@ -605,7 +605,7 @@ jQuery.extend( {
 			if ( s.data && ( s.processData || typeof s.data === "string" ) ) {
 				cacheURL += ( rquery.test( cacheURL ) ? "&" : "?" ) + s.data;
 
-				// #9682: remove data so that it's not used in an eventual retry
+				// trac-9682: remove data so that it's not used in an eventual retry
 				delete s.data;
 			}
 

src/ajax/xhr.js

@@ -66,7 +66,7 @@ jQuery.ajaxTransport( function( options ) {
 						} else if ( type === "error" ) {
 							complete(
 
-								// File: protocol always yields status 0; see #8605, #14207
+								// File: protocol always yields status 0; see trac-8605, trac-14207
 								xhr.status,
 								xhr.statusText
 							);
@@ -99,7 +99,7 @@ jQuery.ajaxTransport( function( options ) {
 				xhr.send( options.hasContent && options.data || null );
 			} catch ( e ) {
 
-				// #14683: Only rethrow if this hasn't been notified as an error yet
+				// trac-14683: Only rethrow if this hasn't been notified as an error yet
 				if ( callback ) {
 					throw e;
 				}

src/attributes/prop.js

@@ -60,7 +60,7 @@ jQuery.extend( {
 				// elem.tabIndex doesn't always return the
 				// correct value when it hasn't been explicitly set
 				// https://web.archive.org/web/20141116233347/http://fluidproject.org/blog/2008/01/09/getting-setting-and-removing-tabindex-values-with-javascript/
-				// Use proper attribute retrieval(#12072)
+				// Use proper attribute retrieval (trac-12072)
 				var tabindex = elem.getAttribute( "tabindex" );
 
 				if ( tabindex ) {

src/attributes/val.js

@@ -149,7 +149,7 @@ if ( isIE ) {
 				val :
 
 				// Support: IE <=10 - 11+
-				// option.text throws exceptions (#14686, #14858)
+				// option.text throws exceptions (trac-14686, trac-14858)
 				// Strip and collapse whitespace
 				// https://html.spec.whatwg.org/#strip-and-collapse-whitespace
 				stripAndCollapse( jQuery.text( elem ) );

src/core/init.js

@@ -10,8 +10,8 @@ import "../traversing/findFilter.js";
 var rootjQuery,
 
 	// A simple way to check for HTML strings
-	// Prioritize #id over <tag> to avoid XSS via location.hash (#9521)
-	// Strict HTML recognition (#11290: must start with <)
+	// Prioritize #id over <tag> to avoid XSS via location.hash (trac-9521)
+	// Strict HTML recognition (trac-11290: must start with <)
 	// Shortcut simple #id case for speed
 	rquickExpr = /^(?:\s*(<[\w\W]+>)[^>]*|#([\w-]+))$/,
 

src/core/ready-no-deferred.js

@@ -25,7 +25,7 @@ jQuery.extend( {
 	isReady: false,
 
 	// A counter to track how many items to wait for before
-	// the ready event fires. See #6781
+	// the ready event fires. See trac-6781
 	readyWait: 1,
 
 	ready: function( wait ) {

src/core/ready.js

@@ -28,7 +28,7 @@ jQuery.extend( {
 	isReady: false,
 
 	// A counter to track how many items to wait for before
-	// the ready event fires. See #6781
+	// the ready event fires. See trac-6781
 	readyWait: 1,
 
 	// Handle when the DOM is ready

src/css.js

@@ -220,15 +220,15 @@ jQuery.extend( {
 		if ( value !== undefined ) {
 			type = typeof value;
 
-			// Convert "+=" or "-=" to relative numbers (#7345)
+			// Convert "+=" or "-=" to relative numbers (trac-7345)
 			if ( type === "string" && ( ret = rcssNum.exec( value ) ) && ret[ 1 ] ) {
 				value = adjustCSS( elem, name, ret );
 
-				// Fixes bug #9237
+				// Fixes bug trac-9237
 				type = "number";
 			}
 
-			// Make sure that null and NaN values aren't set (#7116)
+			// Make sure that null and NaN values aren't set (trac-7116)
 			if ( value == null || value !== value ) {
 				return;
 			}
@@ -239,7 +239,7 @@ jQuery.extend( {
 			}
 
 			// Support: IE <=9 - 11+
-			// background-* props of a cloned element affect the source element (#8908)
+			// background-* props of a cloned element affect the source element (trac-8908)
 			if ( isIE && value === "" && name.indexOf( "background" ) === 0 ) {
 				style[ name ] = "inherit";
 			}

src/css/cssCamelCase.js

@@ -6,7 +6,7 @@ var rmsPrefix = /^-ms-/;
 // Convert dashed to camelCase, handle vendor prefixes.
 // Used by the css & effects modules.
 // Support: IE <=9 - 11+
-// Microsoft forgot to hump their vendor prefix (#9572)
+// Microsoft forgot to hump their vendor prefix (trac-9572)
 function cssCamelCase( string ) {
 	return camelCase( string.replace( rmsPrefix, "ms-" ) );
 }