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Activity - Builds and deployments and are stored in the Activity section. Work item updates such as status changes or uploaded attachments will display here aswell.
Comments - A message can be added to the work item on build or deployments which would display here. The message itself is customized on the project.
Attachments - A relevant files can be added to the work item in this section such as a design document or data. Previews for the attachments are available if the file type is supported.
Commits - If the project is configured for source control, then commits or revisions will display here. The id marked #1 is a link back to the build execution summary and the hash number marked #2 is a link to the commit in the external source control provider if it is supported (i.e. For Git, this would be a Github, Gitlab, Bitbucket commit url).
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