git-gui: Create new branches from a tag.
git-gui: Create new branches from a tag.

I'm missing the possibility to base a new branch on a tag.
The following adds a tag drop down to the new branch dialog.

Signed-off-by: Martin Koegler <ea56f0187842ce0af18f0283b5f003697482ffdd@auto.tuwien.ac.at>
Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git