Merge branch 'js/add-p-leftover-bits'

The final leg of rewriting "add -i/-p" in C.

* js/add-p-leftover-bits:
  ci: include the built-in `git add -i` in the `linux-gcc` job
  built-in add -p: handle Escape sequences more efficiently
  built-in add -p: handle Escape sequences in interactive.singlekey mode
  built-in add -p: respect the `interactive.singlekey` config setting
  terminal: add a new function to read a single keystroke
  terminal: accommodate Git for Windows' default terminal
  terminal: make the code of disable_echo() reusable
  built-in add -p: handle diff.algorithm
  built-in add -p: support interactive.diffFilter
  t3701: adjust difffilter test

diff --cc add-interactive.c
Simple merge

diff --cc t/t3701-add-interactive.sh
Simple merge