Merge branch 'ab/run-command'

API clean-up. * ab/run-command: run-command API: remove "env" member, always use "env_array" difftool: use "env_array" to simplify memory management run-command API: remove "argv" member, always use "args" run-command API users: use strvec_push(), not argv construction run-command API users: use strvec_pushl(), not argv construction run-command tests: use strvec_pushv(), not argv assignment run-command API users: use strvec_pushv(), not argv assignment upload-archive: use regular "struct child_process" pattern worktree: stop being overly intimate with run_command() internals