Add local_git_branch loader

docs/index.md

@@ -46,6 +46,13 @@ migration-lint --loader=local_git --extractor=<your extractor>
 It will examine files in current repository that are added or modified
 and not yet commited.
 
+If you need to check all committed changes in the current branch compared to
+master/main branch (configurable with `CI_DEFAULT_BRANCH`):
+
+```shell linenums="0"
+migration-lint --loader=local_git_branch --extractor=<your extractor>
+```
+
 ### GitLab
 
 If you need to run it on the GitLab pipeline:

migration_lint/source_loader/local.py

@@ -1,5 +1,5 @@
 import os
-from typing import Sequence
+from typing import Any, Sequence
 
 from migration_lint import logger
 from migration_lint.source_loader.base import BaseSourceLoader
@@ -34,3 +34,44 @@ def get_changed_files(self) -> Sequence[SourceDiff]:
             SourceDiff(old_path=diff.a_path, path=diff.b_path)
             for diff in filtered_diffs
         ]
+
+
+class LocalGitBranchLoader(BaseSourceLoader):
+    """A loader to obtain files changed for local committed files since default branch."""
+
+    NAME = "local_git_branch"
+
+    def __init__(
+        self,
+        **kwargs: Any,
+    ) -> None:
+        super().__init__(**kwargs)
+        self.default_branch = os.environ.get("CI_DEFAULT_BRANCH", "master")
+
+    def get_changed_files(self) -> Sequence[SourceDiff]:
+        """Return a list of changed files."""
+
+        from git import Repo
+
+        logger.info(
+            f"### Getting changed files for local commited files since {self.default_branch}"
+        )
+
+        repo = Repo(os.getcwd(), search_parent_directories=True)
+        current_branch = repo.active_branch.name
+        diffs = repo.commit(self.default_branch).diff(repo.commit(current_branch))
+
+        filtered_diffs = [
+            d
+            for d in diffs
+            if not d.deleted_file
+            and (not self.only_new_files or self.only_new_files and d.new_file)
+        ]
+
+        logger.info("Files changed: ")
+        logger.info("\n".join([f"- {d.a_path}" for d in filtered_diffs]))
+
+        return [
+            SourceDiff(old_path=diff.a_path, path=diff.b_path)
+            for diff in filtered_diffs
+        ]