get-prefix

#!/usr/bin/env python3
# Copyright 2016 Kees Cook <keescook@chromium.org>
# License: GPLv2+
#
# Figure out the top 5 most common prefixes used for a given set of files,
# within the last 64 commits touching those files, with the first argument
# being the fall-back when nothing is better.
#
# e.g.
#	$ get-prefix unknown kernel/seccomp.c
#	seccomp:
#	signal:
#	ptrace, seccomp:
#	syscalls:
#	syscall_get_arch:
#
import sys, re, fnmatch, subprocess, operator

debug = False

# Update the copy in split-on-maintainer...
def get_prefixes(area, paths):
	# "--follow" is very slow, but sometime needed:
	#ret = subprocess.run(['git', 'log', '-n', '64', '--no-merges', '--oneline', '--follow', '--'] + paths,
	ret = subprocess.run(['git', 'log', '-n', '64', '--no-merges', '--oneline', '--'] + paths,
			stdout=subprocess.PIPE, check=False)
	commits = str(ret.stdout, 'utf-8').strip().splitlines()
	prefixes = dict()
	for commit in commits:
		title = commit.split(' ', 1)[1].strip()
		# Drop old-style []s
		if '[PATCH]' in title:
			title = title.replace('[PATCH]','').strip()
		if '[' in title:
			prefix = title.partition(']')[0].replace('[','').replace(']','')
			title = title.replace('[%s]' % (prefix), '').strip()
			if not title.startswith(':'):
				prefix += ': '
			title = prefix.lower() + title
		if title.startswith('Revert "'):
			continue
		if ':' in title:
			prefix = title.rpartition(':')[0]
			# Ignore useless prefixes.
			if not prefix in ['net', 'treewide']:
				prefixes.setdefault(prefix, 0.0)
				# Count # of files in commit.
				sha = commit.split(' ', 1)[0].strip()
				wc = subprocess.run(['git', 'show', '--format=', '--name-status', sha],
						stdout=subprocess.PIPE, check=False)
				files = str(wc.stdout, 'utf-8').strip().splitlines()
				divisor = len(files)
				if divisor == 0:
					divisor = 1
				divisor = float(divisor)
				prefixes[prefix] += 1.0 / divisor
	best = 0.0
	prefix = None

	likely = sorted(prefixes.items(), key=operator.itemgetter(1), reverse=True)
	count = len(likely)

	if count == 0:
		print("%s:" % area)
		return

	if count > 5 and not debug:
		count = 5

	for i in range(count):
		if debug:
			print("%f %s:" % (likely[i][1], likely[i][0]))
		else:
			print("%s:" % (likely[i][0]))

if len(sys.argv) > 1:
	get_prefixes(sys.argv[1], sys.argv[2:])
else:
	ret = subprocess.run(['diffstat', '-lp1'],
			stdout=subprocess.PIPE, check=False)
	paths = str(ret.stdout, 'utf-8').strip().splitlines()
	get_prefixes("unknown", paths)