Remove relationship of tracking branch from config via Browse references dialog

By @YueLinHo on April 14, 2015 06:52 (imported from Google Code)

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New feature!

What steps will reproduce the problem?

1. Open Browse references dialog
2. Right click on item which its "Tracked branch" has value
3. Add one more item "Remove tracking branch" in context menu
4. Click "Remove tracking branch" to remove the relationship from config

Related CLI:
git config --unset branch.<branch>.remote
git config --unset branch.<branch>.merge

Ref.
http://git-scm.com/book/en/v2/Git-Branching-Remote-Branches#Tracking-Branches