Sync with 2.14.2

* maint: Git 2.14.2 Git 2.13.6 Git 2.12.5 Git 2.11.4 Git 2.10.5 cvsimport: shell-quote variable used in backticks archimport: use safe_pipe_capture for user input shell: drop git-cvsserver support by default cvsserver: use safe_pipe_capture for `constant commands` as well cvsserver: use safe_pipe_capture instead of backticks cvsserver: move safe_pipe_capture() to the main package