A Python script to check for matching filenames (regardless of path) in the current working directory. I use this as part of a pre-commit hook with git.

detect-filename-clashes.py

#!/usr/bin/env python
"""
Recursively checks that no filenames from the current working directory 
down are the same, even if they are in different subdirectories. Exits 
with status 0 if no matching filenames are found, or 1 if a match is 
found.

"""
import sys,os
print "Checking for filename clashes...",

filenames = []
clashes = []
for root, dirs, files in os.walk('.'):
    if root.startswith('./.git'):
        # Ignore the .git directory.
        continue
    for filename in files:
        if filename.endswith('~'):
            # Ignore automatically created backup files.
            continue
        if os.path.islink(os.path.join(root,filename)):
            # Don't count symlinks as filename clashes.
            continue
        if filename in filenames:
            clashes.append(os.path.join(root,filename))
            filenames.append(filename)
        else:
            filenames.append(filename)

print len(filenames), 'files found...',
if clashes == []:
    print 'OK'
    sys.exit(0)
else:
    print "clash(es) found:"
    for clash in clashes:
        print clash
    sys.exit(1)