Assign a data path and serial number to each test in discover

To support both multihost scenarios and/or running a test multiple
times, tmt needs to distinguish test data directories of different test
instances. To allow this, each test instance is given a "serial number"
which we can use in a data directory name.

Note: there can be more elaborate ways for picking the serial numbers,
the patch starts with something really trivial yet functioning.

Another note: the patch does not isolate tests on a phase level, a
single test, executed on different guests, may still land in the same
data directory. Different patch will solve this issue.

tmt/base.py

@@ -702,6 +702,8 @@ class Test(Core, tmt.export.Exportable['Test']):
     duration: str = DEFAULT_TEST_DURATION_L1
     result: str = 'respect'
 
+    serial_number: int = 0
+
     returncode: Optional[int] = None
     real_duration: Optional[str] = None
     _reboot_count: int = 0

tmt/result.py

@@ -76,6 +76,7 @@ class Result(tmt.utils.SerializableContainer):
     """ Describes what tmt knows about a single test result """
 
     name: str
+    serial_number: Optional[int] = None
     result: ResultOutcome = field(
         default=ResultOutcome.PASS,
         serialize=lambda result: result.value,
@@ -141,6 +142,7 @@ def from_test(
 
         _result = Result(
             name=test.name,
+            serial_number=test.serial_number,
             result=result,
             note=note,
             duration=duration,

tmt/steps/discover/__init__.py

@@ -279,6 +279,12 @@ def go(self) -> None:
             else:
                 raise GeneralError(f'Unexpected phase in discover step: {phase}')
 
+        # TODO: better, more elaborete ways of assigning serial numbers to tests
+        # can be devised - starting with a really trivial one: each test gets
+        # one, starting with `1`.
+        for serial, test in enumerate(self._tests, start=1):
+            test.serial_number = serial
+
         # Show fmf identifiers for tests discovered in plan
         # TODO: This part should go into the 'fmf.py' module
         if self.opt('fmf_id'):

tmt/steps/execute/__init__.py

@@ -200,8 +200,10 @@ def data_path(
         filename not provided) or to the given data file otherwise.
         """
         # Prepare directory path, create if requested
-        assert self.step.workdir is not None
-        directory = self.step.workdir / TEST_DATA / test.name.lstrip('/')
+        assert self.step.workdir is not None  # narrow type
+        directory = self.step.workdir \
+            / TEST_DATA \
+            / f'{test.name.lstrip("/")}-{test.serial_number}'
         if create and not directory.is_dir():
             directory.joinpath(TEST_DATA).mkdir(parents=True)
         if not filename: