Merge branch 'pk/rebase-in-c-5-test'

Rewrite "git rebase" in C.

* pk/rebase-in-c-5-test:
builtin rebase: error out on incompatible option/mode combinations
builtin rebase: use no-op editor when interactive is "implied"
builtin rebase: show progress when connected to a terminal
builtin rebase: fast-forward to onto if it is a proper descendant
builtin rebase: optionally pass custom reflogs to reset_head()
builtin rebase: optionally auto-detect the upstream

diff --cc builtin/rebase.c
Simple merge