Do not check if .git folder exists

git commands will fail anyway if not present

django_migration_linter/migration_linter.py

@@ -134,12 +134,6 @@ class MigrationLinter(object):
     def lint_all_migrations(self, git_commit_id=None):
         # Collect migrations
         if git_commit_id:
-            if not utils.is_git_project(self.django_path):
-                raise ValueError(
-                    (
-                        "The given project {0} does not seem " "to be versioned by git."
-                    ).format(self.django_path)
-                )
             migrations = self._gather_migrations_git(git_commit_id)
         else:
             migrations = self._gather_all_migrations()
@@ -178,7 +172,7 @@ class MigrationLinter(object):
         it allows to seperate the instances correctly.
         """
         sqlmigrate_command = (
-            "cd {0} && " "{1} manage.py sqlmigrate {2} {3} " "--database {4}"
+            "cd {0} && {1} manage.py sqlmigrate {2} {3} " "--database {4}"
         ).format(
             self.django_path, self.python_exe, app_name, migration_name, self.database
         )
@@ -205,7 +199,7 @@ class MigrationLinter(object):
         migrations = []
         # Get changes since specified commit
         git_diff_command = (
-            "cd {0} && " "git diff --name-only --diff-filter=A {1}"
+            "cd {0} && git diff --name-only --diff-filter=A {1}"
         ).format(self.django_path, git_commit_id)
         logger.info("Executing {0}".format(git_diff_command))
         diff_process = Popen(git_diff_command, shell=True, stdout=PIPE, stderr=PIPE)