pipecmd: reverse order of args to match documentation; add pipecmd_preserve.
[ccan] / ccan / pipecmd / test /
drwxr-xr-x   ..
-rw-r--r-- 1188 run-fdleak.c
-rw-r--r-- 2666 run-preserve.c
-rw-r--r-- 4530 run.c