do not setup progress reporter if git is not installed

pyproject.toml

@@ -192,8 +192,9 @@ select = [
 
 [tool.ruff.lint.per-file-ignores]
 "noxfile.py" = ["D", "PTH"]
-"tests/**" = ["S", "ARG001", "ARG002", "ANN"]
+"tests/**" = ["S", "ARG001", "ARG002", "ANN", "TID251", "TID253"]
 "docs/**" = ["INP"]
+"src/scmrepo/git/backend/gitpython.py" = ["TID251"]
 
 [tool.ruff.lint.flake8-pytest-style]
 fixture-parentheses = false
@@ -203,6 +204,14 @@ parametrize-names-type = "csv"
 [tool.ruff.lint.flake8-type-checking]
 strict = true
 
+[tool.ruff.lint.flake8-tidy-imports.banned-api]
+"git".msg = "importing from 'git' is not allowed except inside `gitpython` backend"
+
+[tool.ruff.lint.flake8-tidy-imports]
+# Ban certain modules from being imported at module level, instead requiring
+# that they're imported lazily (e.g., within a function definition).
+banned-module-level-imports = ["git"]
+
 [tool.ruff.lint.isort]
 known-first-party = ["scmrepo"]
 

src/scmrepo/progress.py

@@ -4,7 +4,7 @@
 
 
 def code2desc(op_code):
-    from git import RootUpdateProgress as OP  # noqa: N814
+    from git import RootUpdateProgress as OP  # noqa: N814, TID251
 
     ops = {
         OP.COUNTING: "Counting",
@@ -44,16 +44,20 @@ def parsed_from_gitpython(
 
 class GitProgressReporter:
     def __init__(self, fn) -> None:
-        from git.util import CallableRemoteProgress
-
-        self._reporter = CallableRemoteProgress(self.wrap_fn(fn))
+        try:
+            from git.util import CallableRemoteProgress  # noqa: TID251
+        except ImportError:
+            self._reporter = None
+        else:
+            self._reporter = CallableRemoteProgress(self.wrap_fn(fn))
 
     def __call__(self, msg: Union[str, bytes]) -> None:
-        self._reporter._parse_progress_line(
-            msg.decode("utf-8", errors="replace").strip()
-            if isinstance(msg, bytes)
-            else msg
-        )
+        if self._reporter is not None:
+            self._reporter._parse_progress_line(
+                msg.decode("utf-8", errors="replace").strip()
+                if isinstance(msg, bytes)
+                else msg
+            )
 
     @staticmethod
     def wrap_fn(fn):