Leakfixes. * ps/leakfixes: builtin/mv: fix leaks for submodule gitfile paths builtin/mv: refactor to use `struct strvec` builtin/mv duplicate string list memory builtin/mv: refactor `add_slash()` to always return allocated strings strvec: add functions to replace and remove strings submodule: fix leaking memory for submodule entries commit-reach: fix memory leak in `ahead_behind()` builtin/credential: clear credential before exit config: plug various memory leaks config: clarify memory ownership in `git_config_string()` builtin/log: stop using globals for format config builtin/log: stop using globals for log config convert: refactor code to clarify ownership of check_roundtrip_encoding diff: refactor code to clarify memory ownership of prefixes config: clarify memory ownership in `git_config_pathname()` http: refactor code to clarify memory ownership checkout: clarify memory ownership in `unique_tracking_name()` strbuf: fix leak when `appendwholeline()` fails with EOF transport-helper: fix leaking helper name