Merge branch 'gc/submodule-update-part1'

Rewrite of "git submodule update" in C (early part). * gc/submodule-update-part1: submodule--helper update-clone: check for --filter and --init submodule update: add tests for --filter submodule--helper: remove ensure-core-worktree submodule--helper update-clone: learn --init submodule--helper: allow setting superprefix for init_submodule() submodule--helper: refactor get_submodule_displaypath() submodule--helper run-update-procedure: learn --remote submodule--helper: don't use bitfield indirection for parse_options() submodule--helper: get remote names from any repository submodule--helper run-update-procedure: remove --suboid submodule--helper: reorganize code for sh to C conversion submodule--helper: remove update-module-mode submodule tests: test for init and update failure output