master-side commands only have access to full logfiles

[dustin]

Pradeep worked around this in some clever ways, but master-side source steps' only access to the output of remote commands is .getLogs which (in both tests and real steps) returns the entire set of log outputs, not just those from the most recent command.

We'll need to add a new interface that allows the results of a single command to be analyzed on their own.

[dustin]

I have some work on this (tests, at least) in my bug2095 branch.

[in3xes]

Yes, I did feel the need of such function.

[dustin]

tomprince points me to

 https://github.com/tomprince/buildbot/commit/2ed03c9435065282171607b82f3dcb2b81435618#L0R990

[Dustin J. Mitchell]

Allow command invocations to get stdout back if desired

Fixes #2095.

Changeset: 0d85e971e15530588fad2e59db5fd6b57c2bb560