Merge branch 'jc/ws-error-highlight'

"git diff/log --ws-error-highlight=<kind>" lacked the corresponding configuration variable to set it by default. * jc/ws-error-highlight: diff: introduce diff.wsErrorHighlight option diff.c: move ws-error-highlight parsing helpers up diff.c: refactor parse_ws_error_highlight() t4015: split out the "setup" part of ws-error-highlight test