I hesitate to be this guy, but: If I'm not mistaken, strictly speaking, the mood/mode is imperative, but the tense is present. Imperative is not a tense. In English, there are only two true tenses: past and present.
To disclose fully, I had only a notion of this before resorting to Wikipedia to confirm and provide some clarity. http://en.wikipedia.org/wiki/Grammatical_tense and http://en.wikipedia.org/wiki/Grammatical_mood
That makes more sense (to me) for the example of rebasing - the applied diffs become a list of commands of what to do: Do this! Do that!