Help text for changeset linking as popup

To avoid wrapping of a long text on narrow screens, the details for the
Changeset linking syntax is now displayed as a pop-up when hovering the
mouse over the checkbox's label.

Author: dregad

Source/lang/strings_english.txt

@@ -105,7 +105,8 @@ $s_plugin_Source_show_repo_link = 'Repositories';
 $s_plugin_Source_show_search_link = 'Search';
 $s_plugin_Source_show_repo_stats = 'Repository Statistics';
 $s_plugin_Source_enabled_features = 'Enabled Features';
-$s_plugin_Source_enable_linking = 'Changeset Linking <span class="small">(<em>&lt;type&gt;:&lt;reponame&gt;:&lt;revision&gt;:</em> where &lt;type&gt; = \'s\' for details, \'v\' for diff)</span>';
+$s_plugin_Source_enable_linking = 'Changeset Linking <span class="small">(<em>&lt;type&gt;:&lt;reponame&gt;:&lt;revision&gt;:</em>)';
+$s_plugin_Source_enable_linking_info = 'Where &lt;type&gt = \'c\' or \'s\' for Changeset details; \'d\' or \'v\' for Diff; and \'p\' for Pull Request (if supported by the VCS)';
 $s_plugin_Source_enable_mapping = 'Branch Mappings';
 $s_plugin_Source_enable_resolving = 'Resolve Fixed Issues';
 $s_plugin_Source_enable_message = 'Bug Fixed Message';

Source/pages/manage_config_page.php

@@ -98,8 +98,11 @@
 			</span><br>
 			<span class="">
 				<input type="checkbox" name="enable_linking" <?php
-					check_checked( ON == plugin_config_get( 'enable_linking' ) ) ?>/>
-				<label for="enable_linking"><?php echo plugin_lang_get( 'enable_linking' ) ?></label>
+					check_checked( ON == plugin_config_get( 'enable_linking' ) ) ?>
+					   />
+				<label for="enable_linking"
+					title="<?php echo plugin_lang_get( 'enable_linking_info' ) ?>">
+					<?php echo plugin_lang_get( 'enable_linking' ) ?></label>
 			</span><br>
 			<span class="">
 				<input type="checkbox" name="enable_mapping" <?php