It seems you cannot do this, at least in an obvious way. There are several solutions / workarounds that you can use here:
Choose another favorite terminal. ConEmu is a shell for CMD.exe that will act as your default terminal if you report it [I thought Console2 could do this as well]. Also - forgive the editorial - ConEmu is the way, the way, better than Console2 .
You can add a custom action to the menu. From the global settings, go to the Custom Actions tab and add the action to Open in Terminal using the desired console. It's not as great as just clicking on the terminal icon, but you can easily achieve the same result.
Unfortunately, this is the best that is at the moment.
Note: based on the link that @sendmoreinfo posted, waiting for the addition of Atlassian by default might be the best way for your purposes. The only problem with this may be that according to some of the latest updates of the source tree, they are terrible , so I have not updated it yet.
Note 2: Although this will not do what you want, there is an option in the settings under the Git Tab that allows you to Set Git Bash as default prompt . This may or may not come close to where you want to be.