Fix filenames on a case-sensitive filesystem that would cause collisions on a case-insensitive system (useful for syncthing between Linux and macOS, for example)

case_insensitive_fix.py

import os
import collections
import sys

def rename_case_insensitive_duplicates(directory):
    count = 0
    for dirpath, dirs, files in os.walk(directory):
        # Create dictionaries for filenames and dirnames
        filenames = collections.defaultdict(list)
        dirnames = collections.defaultdict(list)

        for name in files:
            filenames[name.lower()].append(os.path.join(dirpath, name))
        for name in dirs:
            dirnames[name.lower()].append(os.path.join(dirpath, name))

        # Rename files with the same lowercase filename
        for name_list in filenames.values():
            if len(name_list) > 1:
                for i, name in enumerate(name_list):
                    base, ext = os.path.splitext(name)
                    print(f'renaming {name} to {base}_{i}{ext}')
                    os.rename(name, f"{base}_{i}{ext}")
                    count += 1

        # Rename directories with the same lowercase dirname
        for name_list in dirnames.values():
            if len(name_list) > 1:
                for i, name in enumerate(name_list):
                    base = os.path.basename(name)
                    dir = os.path.dirname(name)
                    print(f'renaming {name} to {base}_{i}')
                    os.rename(name, os.path.join(dir, f"{base}_{i}"))
                    count += 1
    print(f"Renamed {count} files and directories")

# Get the directory path from the command line arguments
directory = sys.argv[1]

# Call the function on the directory you want to scan
rename_case_insensitive_duplicates(directory)