Tasktop makes it easy to create links and dependencies between tasks on different repositories in a heterogeneous environment.

To support adding/removing of associations in Bugzilla, the administrator must add a custom field of type Large Text Box with id "cf_task_relations". After this custom field has been added, the actions of the Association section will be visible in the Task Editor.
If you do not see these actions within the Associations section, update the Task Repository configuration in Tasktop via the Task Repositories view. Right click on the task repository in question and select Update Repository Configuration. Synchronize the task and the actions will be available.
Due to limitations of the JIRA API, associations are not as well supported as with Bugzilla. To use associations, you must add a custom field and with the name of "Associations" and give it a default value of ".". The JIRA API does not report the existence of any custom fields which are empty in all tasks, so Tasktop Dev can not recognize the custom field exists. If you do not give the field the default value of ".", then you must add the first association via JIRA's web interface.
Fortunately, the syntax for adding an association is quite simple. Follow the syntax as described below to add your first association. After synchronizing the task in Tasktop, the association will appear. If all associations are removed, you might once again use the web interface.
To add a dependency on a task, select External Dependency from the combo box and paste the URL of the task in the text box. Click the Add button or press enter to add the dependency. If the appropriate repository type cannot be determined, you will be prompted to choose the repository type. After you have selected the repository type, the dependency will appear in the Associations view. To open a dependency, double click or select Open from the popup menu. If the dependency has been added to the Task List, it will open in a Task Editor. Otherwise it will open in a web browser. To remove the dependency, right+click and select Remove. If the dependency appears with a "[Not in Task List]" decoration, you can add it to your Task List using the popup menu. Once added, the task's summary and status will update in the Associations section.
If you want to add a web link to the Associations section, select Web Link from the combo box and paste the url into the text field and click Add. Web links can be removed by selecting the link and choosing Remove from the popup menu.
If the repository supports subtasks, any subtasks present on the task will be presented within the Associations section to aid navigation. Currently, manipulation of subtasks is regulated to the Attribute section above.
This node in the Associations section parses through all content on the task and presents a summary of all tasks/links referenced therein.
Associations are stored in a custom text field on each supported repository. These fields are often visible in the repository's web interface. Users can manipulate associations by editing the simple text format used to denote an association. One association should exist per line of the text field.
To add a dependency on a task within another (or same) repository the syntax is: dependency.[connectorId]: [taskUrl]
Where connectorId is the Mylyn connector id for the given repository type:
Where taskUrl is the web addressable url of the task.
To add a web link the syntax is: link.web: [web addressable url]