Merge branch 'ms/refs-list'

The "list" subcommand of "git refs" acts as a front-end for "git for-each-ref". * ms/refs-list: t: add test for git refs list subcommand t6300: refactor tests to be shareable builtin/refs: add list subcommand builtin/for-each-ref: factor out core logic into a helper builtin/for-each-ref: align usage string with the man page doc: factor out common option