Merge branch 'js/run-command-updates'
* js/run-command-updates:
api-run-command.txt: describe error behavior of run_command functions
run-command.c: squelch a "use before assignment" warning
receive-pack: remove unnecessary run_status report
run_command: report failure to execute the program, but optionally don't
run_command: encode deadly signal number in the return value
run_command: report system call errors instead of returning error codes
run_command: return exit code as positive value
MinGW: simplify waitpid() emulation macros