ShellMixin: workdir should be overridable

This is a port from eight.

master/buildbot/process/buildstep.py

@@ -1126,7 +1126,8 @@ def makeRemoteShellCommand(self, collectStdout=False, collectStderr=False,
         kwargs['env'].update(self.env)
         kwargs['stdioLogName'] = stdioLogName
 
-        kwargs['workdir'] = self.workdir
+        if not kwargs.get('workdir'):
+            kwargs['workdir'] = self.workdir
 
         # the rest of the args go to RemoteShellCommand
         cmd = remotecommand.RemoteShellCommand(

master/buildbot/test/unit/test_process_buildstep.py

@@ -822,13 +822,15 @@ def run(self):
 
 class SimpleShellCommand(buildstep.ShellMixin, buildstep.BuildStep):
 
-    def __init__(self, **kwargs):
+    def __init__(self, makeRemoteShellCommandKwargs=None, **kwargs):
+        self.makeRemoteShellCommandKwargs = makeRemoteShellCommandKwargs or {}
+
         kwargs = self.setupShellMixin(kwargs)
         buildstep.BuildStep.__init__(self, **kwargs)
 
     @defer.inlineCallbacks
     def run(self):
-        cmd = yield self.makeRemoteShellCommand()
+        cmd = yield self.makeRemoteShellCommand(**self.makeRemoteShellCommandKwargs)
         yield self.runCommand(cmd)
         defer.returnValue(cmd.results())
 
@@ -922,6 +924,19 @@ def test_example_step_workdir(self):
         self.expectOutcome(result=SUCCESS)
         yield self.runStep()
 
+    @defer.inlineCallbacks
+    def test_example_override_workdir(self):
+        # Test that makeRemoteShellCommand(workdir=X) works.
+        self.setupStep(SimpleShellCommand(
+            makeRemoteShellCommandKwargs={'workdir': '/alternate'},
+            command=['foo', properties.Property('bar', 'BAR')]))
+        self.expectCommands(
+            ExpectShell(workdir='/alternate', command=['foo', 'BAR'])
+            + 0,
+        )
+        self.expectOutcome(result=SUCCESS)
+        yield self.runStep()
+
     @defer.inlineCallbacks
     def test_example_env(self):
         self.setupStep(ShellMixinExample(env={'BAR': 'BAR'}), wantDefaultWorkdir=False)