Add check-merge-conflict hook

pre_commit_hooks/check_merge_conflict.py

@@ -0,0 +1,31 @@
+from __future__ import print_function
+
+import argparse
+import sys
+
+CONFLICT_PATTERNS = [
+    '<<<<<<< ',
+    '=======',
+    '>>>>>>> '
+]
+WARNING_MSG = 'Merge conflict string "{0}" found in {1}:{2}'
+
+
+def detect_merge_conflict(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*')
+    args = parser.parse_args(argv)
+
+    retcode = 0
+    for filename in args.filenames:
+        with open(filename) as inputfile:
+            for i, line in enumerate(inputfile):
+                for pattern in CONFLICT_PATTERNS:
+                    if line.startswith(pattern):
+                        print(WARNING_MSG.format(pattern, filename, i))
+                        retcode = 1
+
+    return retcode
+
+if __name__ == '__main__':
+    sys.exit(detect_merge_conflict())