git-completion.bash: zsh does not implement function redirection correctly

A recent change added functions whose entire standard error stream is redirected to /dev/null using a construct that is valid POSIX.1 but is not widely used: funcname () { cd "$1" && run some command "$2" } 2>/dev/null Even though this file is "git-completion.bash", zsh completion support dot-sources it (instead of asking bash to grok it like tcsh completion does), and zsh does not implement this redirection correctly. With zsh, trying to complete an inexistant directory gave this: git add no-such-dir/__git_ls_files_helper:cd:2: no such file or directory: no-such-dir/ Also these functions use "cd" to first go somewhere else before running a command, but the location the caller wants them to go that is given as an argument to them should not be affected by CDPATH variable the users may have set for their interactive session. To fix both of these, wrap the body of the function in a subshell, unset CDPATH at the beginning of the subshell, and redirect the standard error stream of the subshell to /dev/null. Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr> Signed-off-by: Junio C Hamano <gitster@pobox.com>