As noted in commit 548ec7045 (win32: interpret absolute paths as relative to %SYSTEMDRIVE%) a path starting with a '/' in the Unix world is treated as relative to the current drive by Windows. To avoid ambiguity that commit considered certain such paths to be relative to %SYSTEMDRIVE%. Extend this to paths representing executables. Add the functions need_system_drive() and auto_add_system_drive() to detect the need for a system drive prefix and to add it if necessary. Use these functions in: - the 'which' applet - the find_executable() function - tab-completion code - PATH look-up, shellexec(), describe_command() and find_command() in ash - parse_interpreter() and mingw_spawn_1() With these changes executable paths starting with a slash are handled consistently, whatever the current drive.