Merge branch 'ab/help-fixes'

Updates to how command line options to "git help" are handled. * ab/help-fixes: help: don't print "\n" before single-section output help: add --no-[external-commands|aliases] for use with --all help: error if [-a|-g|-c] and [-i|-m|-w] are combined help: correct usage & behavior of "git help --all" help: note the option name on option incompatibility help.c: split up list_all_cmds_help() function help tests: test "git" and "git help [-a|-g] spacing help.c: use puts() instead of printf{,_ln}() for consistency help doc: add missing "]" to "[-a|--all]"