Pull non-default branch commits selectively (elastic#1879)

After switching Elasticsearch nightly benchmarks to non-default branch
it was observed `branch@timestamp` notation in `--revision` command line
flag does not guarantee constant results due to ongoing merges from
default branch (`main`) into non-default branch. Specifically, if a
merge from main brought in a commit that happened before `timestamp`,
such commit might be selected despite not being part of non-default
branch.

This change mitigates this problem by filtering commit IDs of default
branch (`main`) using `main..branch` notation of `git rev-list` command.

esrally/mechanic/supplier.py

@@ -750,7 +750,7 @@ def _update(self, revision):
                 branch,
                 self.name,
             )
-            git.pull_ts(self.src_dir, git_ts_revision, remote="origin", branch=branch)
+            git.pull_ts(self.src_dir, git_ts_revision, remote="origin", branch=branch, default_branch=DEFAULT_ELASTICSEARCH_BRANCH)
         elif self.has_remote():  # we can have either a commit hash, branch name, or tag
             git.fetch(self.src_dir, remote="origin")
             if git.is_branch(self.src_dir, identifier=revision):

esrally/utils/git.py

@@ -105,10 +105,14 @@ def pull(src_dir, *, remote, branch):
 
 
 @probed
-def pull_ts(src_dir, ts, *, remote, branch):
+def pull_ts(src_dir, ts, *, remote, branch, default_branch):
     fetch(src_dir, remote=remote)
     clean_src = io.escape_path(src_dir)
-    rev_list_command = f'git -C {clean_src} rev-list -n 1 --before="{ts}" --date=iso8601 {remote}/{branch}'
+    # non-default ES branches might receive merges from default ES branch which we want to filter out
+    if branch != default_branch:
+        rev_list_command = f'git -C {clean_src} rev-list -n 1 --before="{ts}" --date=iso8601 {remote}/{default_branch}..{remote}/{branch}'
+    else:
+        rev_list_command = f'git -C {clean_src} rev-list -n 1 --before="{ts}" --date=iso8601 {remote}/{branch}'
     revision = process.run_subprocess_with_output(rev_list_command)[0].strip()
     if process.run_subprocess_with_logging(f"git -C {clean_src} checkout {revision}"):
         raise exceptions.SupplyError("Could not checkout source tree for timestamped revision [%s]" % ts)

tests/mechanic/supplier_test.py

@@ -147,7 +147,7 @@ def test_checkout_ts(self, mock_is_working_copy, mock_pull_ts, mock_head_revisio
         s.fetch("@2023-04-20T11:09:12Z")
 
         mock_is_working_copy.assert_called_with("/src")
-        mock_pull_ts.assert_called_with("/src", "2023-04-20T11:09:12Z", remote="origin", branch="main")
+        mock_pull_ts.assert_called_with("/src", "2023-04-20T11:09:12Z", remote="origin", branch="main", default_branch="main")
         mock_head_revision.assert_called_with("/src")
 
     @mock.patch("esrally.utils.git.fetch", autospec=True)

tests/utils/git_test.py

@@ -42,6 +42,7 @@ def setup(request, tmp_path_factory):
     cls.local_remote_name = "remote_repo"
     cls.local_branch = "rally-unit-test-local-only-branch"
     cls.remote_branch = "rally-unit-test-remote-only-branch"
+    cls.remote_branch_non_master = "rally-unit-test-remote-only-branch-non-master"
     cls.rebase_branch = "rally-unit-test-rebase-branch"
 
     cls.local_tmp_src_dir = str(tmp_path_factory.mktemp("rally-unit-test-local-dir"))
@@ -70,8 +71,16 @@ def setup(request, tmp_path_factory):
     cls.old_revision = cls.remote_repo.heads["master"].commit.hexsha
     commit(cls.remote_repo)
     cls.remote_branch_hash = cls.remote_repo.heads["master"].commit.hexsha
-
     cls.remote_repo.create_head(cls.remote_branch, "HEAD")
+
+    # create branch not aligned with master
+    non_master_branch = cls.remote_repo.create_head(cls.remote_branch_non_master, cls.old_revision)
+    cls.remote_repo.head.reference = non_master_branch
+    cls.remote_repo.head.reset(index=True, working_tree=True)
+    commit(cls.remote_repo, date="2016-01-01 01:00:00+0000")
+    cls.remote_branch_non_master_hash = cls.remote_repo.heads[cls.remote_branch_non_master].commit.hexsha
+    commit(cls.remote_repo)
+
     cls.local_repo.create_remote(cls.local_remote_name, cls.remote_tmp_src_dir)
     cls.local_repo.remotes[cls.local_remote_name].fetch()
 
@@ -185,8 +194,14 @@ def test_head_revision(self):
 
     def test_pull_ts(self):
         # minimum 'core.abbrev' is to return 7 char prefixes
-        git.pull_ts(self.local_tmp_src_dir, "2016-01-01T110000Z", remote=self.local_remote_name, branch=self.remote_branch)
-        assert git.head_revision(self.local_tmp_src_dir).startswith(self.old_revision)
+        git.pull_ts(
+            self.local_tmp_src_dir,
+            "2016-01-01T110000Z",
+            remote=self.local_remote_name,
+            branch=self.remote_branch_non_master,
+            default_branch="master",
+        )
+        assert git.head_revision(self.local_tmp_src_dir).startswith(self.remote_branch_non_master_hash)
 
     def test_rebase(self, setup_teardown_rebase):
         # fetch required first to get remote branch