check cygwin mismatch earlier

pre_commit/clientlib.py

@@ -13,7 +13,7 @@ from identify.identify import ALL_TAGS
 
 import pre_commit.constants as C
 from pre_commit.color import add_color_option
-from pre_commit.error_handler import FatalError
+from pre_commit.errors import FatalError
 from pre_commit.languages.all import all_languages
 from pre_commit.logging_handler import logging_handler
 from pre_commit.util import parse_version

pre_commit/error_handler.py

@@ -7,14 +7,11 @@ from typing import Generator
 
 import pre_commit.constants as C
 from pre_commit import output
+from pre_commit.errors import FatalError
 from pre_commit.store import Store
 from pre_commit.util import force_bytes
 
 
-class FatalError(RuntimeError):
-    pass
-
-
 def _log_and_exit(msg: str, exc: BaseException, formatted: str) -> None:
     error_msg = f'{msg}: {type(exc).__name__}: '.encode() + force_bytes(exc)
     output.write_line_b(error_msg)

pre_commit/errors.py

@@ -0,0 +1,2 @@
+class FatalError(RuntimeError):
+    pass

pre_commit/git.py

@@ -6,6 +6,8 @@ from typing import List
 from typing import Optional
 from typing import Set
 
+from pre_commit.errors import FatalError
+from pre_commit.util import CalledProcessError
 from pre_commit.util import cmd_output
 from pre_commit.util import cmd_output_b
 from pre_commit.util import EnvironT
@@ -43,7 +45,21 @@ def no_git_env(_env: Optional[EnvironT] = None) -> Dict[str, str]:
 
 
 def get_root() -> str:
-    return cmd_output('git', 'rev-parse', '--show-toplevel')[1].strip()
+    try:
+        root = cmd_output('git', 'rev-parse', '--show-toplevel')[1].strip()
+    except CalledProcessError:
+        raise FatalError(
+            'git failed. Is it installed, and are you in a Git repository '
+            'directory?',
+        )
+    else:
+        if root == '':  # pragma: no cover (old git)
+            raise FatalError(
+                'git toplevel unexpectedly empty! make sure you are not '
+                'inside the `.git` directory of your repository.',
+            )
+        else:
+            return root
 
 
 def get_git_dir(git_root: str = '.') -> str:
@@ -181,7 +197,7 @@ def check_for_cygwin_mismatch() -> None:
     """See https://github.com/pre-commit/pre-commit/issues/354"""
     if sys.platform in ('cygwin', 'win32'):  # pragma: no cover (windows)
         is_cygwin_python = sys.platform == 'cygwin'
-        toplevel = cmd_output('git', 'rev-parse', '--show-toplevel')[1]
+        toplevel = get_root()
         is_cygwin_git = toplevel.startswith('/')
 
         if is_cygwin_python ^ is_cygwin_git:

pre_commit/main.py

@@ -23,10 +23,8 @@ from pre_commit.commands.run import run
 from pre_commit.commands.sample_config import sample_config
 from pre_commit.commands.try_repo import try_repo
 from pre_commit.error_handler import error_handler
-from pre_commit.error_handler import FatalError
 from pre_commit.logging_handler import logging_handler
 from pre_commit.store import Store
-from pre_commit.util import CalledProcessError
 
 
 logger = logging.getLogger('pre_commit')
@@ -146,21 +144,8 @@ def _adjust_args_and_chdir(args: argparse.Namespace) -> None:
     if args.command == 'try-repo' and os.path.exists(args.repo):
         args.repo = os.path.abspath(args.repo)
 
-    try:
-        toplevel = git.get_root()
-    except CalledProcessError:
-        raise FatalError(
-            'git failed. Is it installed, and are you in a Git repository '
-            'directory?',
-        )
-    else:
-        if toplevel == '':  # pragma: no cover (old git)
-            raise FatalError(
-                'git toplevel unexpectedly empty! make sure you are not '
-                'inside the `.git` directory of your repository.',
-            )
-        else:
-            os.chdir(toplevel)
+    toplevel = git.get_root()
+    os.chdir(toplevel)
 
     args.config = os.path.relpath(args.config)
     if args.command in {'run', 'try-repo'}:
@@ -339,11 +324,11 @@ def main(argv: Optional[Sequence[str]] = None) -> int:
         parser.parse_args(['--help'])
 
     with error_handler(), logging_handler(args.color):
+        git.check_for_cygwin_mismatch()
+
         if args.command not in COMMANDS_NO_GIT:
             _adjust_args_and_chdir(args)
 
-        git.check_for_cygwin_mismatch()
-
         store = Store()
         store.mark_config_used(args.config)