Merge branch 'jn/help-everywhere'

* jn/help-everywhere: (23 commits) diff --no-index: make the usage string less scary merge-{recursive,subtree}: use usagef() to print usage Introduce usagef() that takes a printf-style format Let 'git <command> -h' show usage without a git dir Show usage string for 'git http-push -h' Let 'git http-fetch -h' show usage outside any git repository Show usage string for 'git stripspace -h' Show usage string for 'git unpack-file -h' Show usage string for 'git show-index -h' Show usage string for 'git rev-parse -h' Show usage string for 'git merge-one-file -h' Show usage string for 'git mailsplit -h' Show usage string for 'git imap-send -h' Show usage string for 'git get-tar-commit-id -h' Show usage string for 'git fast-import -h' Show usage string for 'git check-ref-format -h' http-fetch: add missing initialization of argv0_path Show usage string for 'git show-ref -h' Show usage string for 'git merge-ours -h' Show usage string for 'git commit-tree -h' ... Conflicts: imap-send.c