Highlighting added/deleted lines, ignoring moves, in a patch file

Question

I'm reviewing a patch that moved a lot of things around, added a few things, and removed a few things. I'm wondering if anyone's written a utility for picking out the unique adds/removes in a universal diff?

That is, an add and a remove of the same line should cancel themselves out.

Obviously this isn't useful all the time, but sometimes it's exactly what I want :)

Answer 1

Use the Pretty Diff tool to visually see such changes. It highlights differences per line and then per character on those lines. It also shows blocks of lines that have been removed in red or blocks in green that have been added. It has a side by side diff mode or a top-down inline diff mode.

http://mailmarkup.org/prettydiff/prettydiff.html

Answer 2

This is what I ended up using.

Example usage:

git diff -w | /path/to/ignore_moves.py | less -R

ignore_moves.py

#!/usr/bin/python                                                                                                             

import sys
from itertools import *

RED = 31
GREEN = 32

RESET_SEQ = "\033[0m"
COLOR_SEQ = "\033[0;%dm"

stack = []

def inverse(line):
    return ('-' if line[0] == '+' else '+') + line[1:].strip()

def reverse_enumerate(l):
    for i, x in enumerate(reversed(l)):
        yield len(l)-1-i, x

def dumpchanges():
    for line in stack:
        SEQ = COLOR_SEQ % (GREEN if line.startswith('+') else RED)
        print SEQ + line.strip() + RESET_SEQ
    stack[:] = []

for line in sys.stdin.readlines():
    if not line[1:].strip():
        continue # ignore empty lines                                                                                         
    if line.startswith(('---', '+++')):
        dumpchanges()
        print line.strip()
    elif line.startswith(('+', '-')):
        inverted = inverse(line)
        line = line[0] + line[1:].strip()
        for i, match in reverse_enumerate(stack):
            if inverted == match:
                stack.pop(i)
                break
        else:
            stack.append(line)

# finished reading, still have state to be dumped                                                                             
dumpchanges()