Add support for config files

gitlint

 #!/usr/bin/env python3
 
-from os import path
+import json
+import pathlib
 import shlex
 import subprocess
 import sys
 import termios
 
 
-linters = {
+DEFAULT_LINTERS = {
     'js': ('eslint', '--stdin'),
     'py': ('flake8', '--ignore=E121,E123,E126,E266,E501,E704,E731', '-'),
     'scss': ('scss-lint', '--stdin-file-path', '{filename}', '-'),
 }
 
 
+class InvalidLinterConfigError(Exception):
+    def __init__(self, path):
+        self.path = path
+
+
 class NoLinterFound(Exception):
     pass
 
@@ -79,6 +85,22 @@ class Terminal:
         termios.tcsetattr(fd, termios.TCSAFLUSH, attrs)
 
 
+def find_git_project_root():
+    path = pathlib.Path.cwd()
+
+    while True:
+        parent = path.parent
+        if path == parent:
+            break
+
+        if (path / '.git').exists():
+            return path
+
+        path = parent
+
+    return None
+
+
 def get_files():
     files = []
 
@@ -88,27 +110,53 @@ def get_files():
             break
 
         filename = line.strip()
-        files.append(filename)
+        files.append(pathlib.Path(filename))
 
     return files
 
 
-def get_linter(filename):
+def get_linter(linters, filename):
+    extension = filename.suffix[1:]
     try:
-        _, extension = filename.rsplit('.', 1)
         linter_args = linters[extension]
-    except (KeyError, ValueError):
+    except KeyError:
         raise NoLinterFound
 
     return (arg.format(filename=filename) for arg in linter_args)
 
 
-def lint(filename, require_linter=False):
-    if not path.exists(filename):
+def get_linter_config(config_filename='.gitlint.json'):
+    git_root = find_git_project_root()
+    if git_root:
+        config = git_root / config_filename
+        if config.exists():
+            return config
+
+    config = pathlib.Path.home() / config_filename
+    if config.exists():
+        return config
+
+    return None
+
+
+def get_linters():
+    config = get_linter_config()
+    if config:
+        try:
+            with config.open() as f:
+                return json.load(f)
+        except (json.JSONDecodeError, OSError):
+            raise InvalidLinterConfigError(config)
+
+    return DEFAULT_LINTERS
+
+
+def lint(linters, filename, require_linter=False):
+    if not filename.exists():
         return True
 
     try:
-        linter_args = get_linter(filename)
+        linter_args = get_linter(linters, filename)
     except NoLinterFound:
         print('No linter found for', filename, file=sys.stderr)
         return not require_linter
@@ -121,14 +169,14 @@ def lint(filename, require_linter=False):
     return ret == 0
 
 
-def lint_all(files):
+def lint_all(linters, files):
     success = False
 
     while not success:
         success = True
 
         for filename in files:
-            success &= lint(filename)
+            success &= lint(linters, filename)
 
         if not success:
             retry, skip = prompt_for_retry()
@@ -174,9 +222,15 @@ def main():
     for signum in exit_signals:
         signal(signum, sig_handler)
 
+    try:
+        linters = get_linters()
+    except InvalidLinterConfigError as e:
+        print('Cannot read linter config: %s' % e.path, file=sys.stderr)
+        return 1
+
     try:
         files = get_files()
-        success = lint_all(files)
+        success = lint_all(linters, files)
     except Exit:
         success = False