Merge branch 'sp/runtime-prefix'

* sp/runtime-prefix: Windows: Revert to default paths and convert them by RUNTIME_PREFIX Compute prefix at runtime if RUNTIME_PREFIX is set Modify setup_path() to only add git_exec_path() to PATH Add calls to git_extract_argv0_path() in programs that call git_config_* git_extract_argv0_path(): Move check for valid argv0 from caller to callee Refactor git_set_argv0_path() to git_extract_argv0_path() Move computation of absolute paths from Makefile to runtime (in preparation for RUNTIME_PREFIX)