branch.spec.ts too strict

[duncdrum]

1) branch
       only master branch after first commit:

      AssertionError: expected 'main' to equal 'master'
      + expected - actual

      -main
      +master
      
      at Object.<anonymous> (src/command/branch.spec.ts:60:45)
      at step (src/command/branch.spec.ts:32:23)
      at Object.next (src/command/branch.spec.ts:13:53)
      at fulfilled (src/command/branch.spec.ts:4:58)
      at processTicksAndRejections (internal/process/task_queues.js:97:5)

https://github.com/theia-ide/dugite-extra/blob/f7e9a1ab65ad60370d5dfbb3104b14e2db1c795d/src/command/branch.spec.ts#L55

with the switch to main as the default branch name, that test will fail on many systems. At a minimum either main or master should be acceptable. ultimately i m not yet sure why the name of the branch is checked here at all, as it is use configurable, so maybe the logic should be changed to actually test for any name to be returned or more in line with the description the total number of branches to be 1.

the same problem is repeated for https://github.com/theia-ide/dugite-extra/blob/f7e9a1ab65ad60370d5dfbb3104b14e2db1c795d/src/command/branch.spec.ts#L75
and
https://github.com/theia-ide/dugite-extra/blob/f7e9a1ab65ad60370d5dfbb3104b14e2db1c795d/src/command/branch.spec.ts#L91