Fix test

nava/platform/util/git.py

@@ -92,8 +92,16 @@ def tag(self, tag: str) -> None:
     def rename_branch(self, new_branch_name: str) -> None:
         self._run_cmd(["git", "branch", "-m", new_branch_name])
 
-    def get_commit_hash_for_head(self) -> str:
-        return self._run_cmd(["git", "rev-parse", "HEAD"]).stdout.strip()
+    def get_commit_hash_for_head(self) -> str | None:
+        result = self._run_cmd(["git", "rev-parse", "HEAD"])
+
+        # say you run this against an empty repo, you'll get a return code of
+        # 128 and message "fatal: ambiguous argument 'HEAD': unknown revision or
+        # path not in the working tree."
+        if result.returncode != 0:
+            return None
+
+        return result.stdout.strip()
 
     def is_path_ignored(self, path: str) -> bool:
         result = self._run_cmd(["git", "check-ignore", "-q", path])
@@ -135,6 +143,14 @@ def get_commit_description(self, commit_ish: str = "HEAD") -> str | None:
 
         return result.stdout.strip()
 
+    def get_commit_count(self, ref: str = "HEAD") -> int | None:
+        result = self._run_cmd(["git", "rev-list", "--count", ref])
+
+        if result.returncode != 0:
+            return None
+
+        return int(result.stdout.strip())
+
 
 def is_a_git_worktree(dir: Path) -> bool:
     result = run_text(

tests/projects/test_migrate_from_legacy_template.py

@@ -29,14 +29,27 @@ def new_template_dir_with_git(tmp_path: Path) -> GitProject:
     return new_dir_with_git(tmp_path / "template")
 
 
+@pytest.fixture
+def new_template_dir_with_git_and_content(new_template_dir_with_git: GitProject) -> GitProject:
+    template_git = new_template_dir_with_git
+
+    (template_git.dir / "foo.txt").write_text("bar")
+    template_git.commit_all("Initial commit")
+
+    return template_git
+
+
 @pytest.fixture
 def legacy_project_dir_with_git(
-    new_project_dir_with_git: GitProject, new_template_dir_with_git: GitProject
+    new_project_dir_with_git: GitProject, new_template_dir_with_git_and_content: GitProject
 ) -> GitProject:
+    template_git = new_template_dir_with_git_and_content
+
     (new_project_dir_with_git.dir / ".template-version").write_text(
-        new_template_dir_with_git.get_commit_hash_for_head()
+        template_git.get_commit_hash_for_head() or "foobar"
     )
     new_project_dir_with_git.commit_all("Legacy install")
+
     return new_project_dir_with_git
 
 
@@ -64,7 +77,7 @@ def test_migrate_from_legacy_no_commit(
     cli_context: CliContext,
 ):
     project = Project(legacy_project_dir_with_git.dir)
-    commit_count_before = len(project.git.log().stdout.splitlines())
+    commit_count_before = project.git.get_commit_count()
 
     MigrateFromLegacyTemplate(
         ctx=cli_context,
@@ -73,7 +86,7 @@ def test_migrate_from_legacy_no_commit(
         new_version_answers_file_name="foo.yml",
     ).migrate_from_legacy(commit=False)
 
-    commit_count_after = len(project.git.log().stdout.splitlines())
+    commit_count_after = project.git.get_commit_count()
 
     # only new file should exist
     assert (project.dir / ".template" / "foo.yml").exists()
@@ -88,7 +101,7 @@ def test_migrate_from_legacy_commit(
     cli_context: CliContext,
 ):
     project = Project(legacy_project_dir_with_git.dir)
-    commit_count_before = len(project.git.log().stdout.splitlines())
+    commit_count_before = project.git.get_commit_count() or 0
 
     MigrateFromLegacyTemplate(
         ctx=cli_context,
@@ -97,7 +110,7 @@ def test_migrate_from_legacy_commit(
         new_version_answers_file_name="foo.yml",
     ).migrate_from_legacy(commit=True)
 
-    commit_count_after = len(project.git.log().stdout.splitlines())
+    commit_count_after = project.git.get_commit_count()
 
     # only new file should exist
     assert (project.dir / ".template" / "foo.yml").exists()