Merge branch 'js/cherry-pick-usability'

* js/cherry-pick-usability:
Teach commit about CHERRY_PICK_HEAD
bash: teach __git_ps1 about CHERRY_PICK_HEAD
Introduce CHERRY_PICK_HEAD
t3507: introduce pristine-detach helper

diff --cc Documentation/git-cherry-pick.txt
Simple merge

diff --cc Documentation/git-commit.txt
Simple merge

diff --cc builtin/commit.c
Simple merge

diff --cc builtin/merge.c
Simple merge

diff --cc builtin/revert.c
Simple merge

diff --cc wt-status.c
Simple merge