Added end of file fixer hook.

pre_commit_hooks/end_of_file_fixer.py

@@ -0,0 +1,70 @@
+
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import argparse
+import os
+import sys
+
+from pre_commit_hooks.util import entry
+
+
+def fix_file(file_obj):
+    # Test for newline at end of file
+    # Empty files will throw IOError here
+    try:
+        file_obj.seek(-1, os.SEEK_END)
+    except IOError:
+        return 0
+    last_character = file_obj.read(1)
+    # last_character will be '' for an empty file
+    if last_character != '\n' and last_character != '':
+        file_obj.write('\n')
+        return 1
+
+    while last_character == '\n':
+        # Deal with the beginning of the file
+        if file_obj.tell() == 1:
+            # If we've reached the beginning of the file and it is all
+            # linebreaks then we can make this file empty
+            file_obj.seek(0)
+            file_obj.truncate()
+            return 1
+
+        # Go back two bytes and read a character
+        file_obj.seek(-2, os.SEEK_CUR)
+        last_character = file_obj.read(1)
+
+    # Our current position is at the end of the file just before any amount of
+    # newlines.  If we read two characters and get two newlines back we know
+    # there are extraneous newlines at the ned of the file.  Then backtrack and
+    # trim the end off.
+    if len(file_obj.read(2)) == 2:
+        file_obj.seek(-1, os.SEEK_CUR)
+        file_obj.truncate()
+        return 1
+
+    return 0
+
+
+@entry
+def end_of_file_fixer(argv):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='Filenames to fix')
+    args = parser.parse_args(argv)
+
+    retv = 0
+
+    for filename in args.filenames:
+        # Read as binary so we can read byte-by-byte
+        with open(filename, 'rb+') as file_obj:
+            ret_for_file = fix_file(file_obj)
+            if ret_for_file:
+                print('Fixing {0}'.format(filename))
+            retv |= ret_for_file
+
+    return retv
+
+
+if __name__ == '__main__':
+    sys.exit(end_of_file_fixer())