Merge branch 'js/builtin-rebase-perf-fix'

Code clean-up with correction to make the reimplemented "git
rebase" a more faithful rewrite of the original, which also regains
performance.

* js/builtin-rebase-perf-fix:
built-in rebase: reinstate `checkout -q` behavior where appropriate
rebase: prepare reset_head() for more flags
rebase: consolidate clean-up code before leaving reset_head()

diff --cc builtin/rebase.c
Simple merge