TFS 2017 | VSTS
A task group lets you to encapsulate a sequence of tasks already defined in a build or a release definition into a single reusable task that can be added to a build or release definition, just like any other task. You can choose to extract the parameters from the encapsulated tasks as configuration variables, and abstract the rest of the task information.
The new task group is automatically added to the task catalogue, ready to add to other release and build definitions. Task groups are stored at project level, and are not accessible outside the project scope.
Task groups are a way to standardize and centrally manage deployment steps for all your applications. When you include a task group in your definitions, and then make a change centrally to the task group, the change is automatically reflected in all the definitions that use the task group. There is no need to change each one individually.
To create a task group, selecting a sequence of tasks in a build or release definition (when using a mouse, click on the checkmarks of each one). Then open the shortcut menu and choose Create task group. Specify a name and description, and the category (tab) you want to add it to in the Add tasks dialog.
However, before you do that, consider the following pointers to help you achieve the desired behavior:
Ensure that all of the tasks you want to include in a task group have their parameters defined as variables, such as $(MyVariable), where you want to be able to configure these parameters when you use the task group. Variables used in the tasks are automatically extracted and converted into parameters for the task group. Values of these configuration variables will be converted into default values for the task group.
If you specify a value (instead of a variable) for a parameter, that value becomes a fixed parameter value and cannot be exposed as a parameter to the task group.
Parameters of the encapsulated tasks for which you specified a value (instead of a variable), or you didn't provide a value for, are not configurable in the task group when added to a build or release definition.
When you save the task group, you can provide a name and a description for the new task group, and select a category where you want it to appear in the Task catalog dialog. You can also change the default values for each of the parameters.
When you queue a build or a deployment, the encapsulated tasks are extracted and the values you entered for the task group parameters are applied to the tasks.
Changes you make to a task group are reflected in every instance of the task group.
All the task groups you create in the current project are listed in the Task groups tab of the Build & Release hub.
In the Properties page you can edit details of the task group, and change the default values and descriptions for the parameters.
In the Tasks page you can edit the tasks that make up the task group. For each encapsulated task you can change the parameter values for the non-variable parameters, edit the existing parameter variables, or convert parameter values to and from variables.
In the History tab you can see the history of changes to the group.
In the References tab you can expand lists of all the release definitions, build definitions, and other task groups that use (reference) this task group. This is useful to ensure changes do not have unexpected effects on other processes.
You can import and export a task group as a JSON file.