Fix EchoQuotedArgsUnix/AssertEchoArgs

[axw]

The EchoQuotedArgsUnix script writes
a file to record the command line arguments
of the process. The script was using
the basename, which only works as
expected if the command is run in the
CWD set at the time of the AssertEchoArgs
call.

Instead of this, write to the location
of the script + ".out", and then read
from the same location in AssertEchoArgs
using os/exec.LookPath. We also introduce
ReadEchoArgs to fetch the value without
checking its contents.

[jameinel]

why is ReadEchoArgs also an exposed function? It seems very tied to having the content put into a '.out' file which is only really assured by AssertEchoArgs, isn't it?

[axw]

why is ReadEchoArgs also an exposed function?

Because the arg values may be partially non-deterministic. e.g. in my case, one of the args is a temporary directory.

It seems very tied to having the content put into a '.out' file which is only really assured by AssertEchoArgs, isn't it?

They provide the same assurances. AssertEchoArgs defers most of the work to ReadEchoArgs.

[axw]

$$merge$$

[jujubot]

Status: merge request accepted. Url: http://juju-ci.vapour.ws:8080/job/github-merge-juju-testing