VIM as a Diff/Merge Tool

Tim Ottinger — Wed, 30 Apr 2008 21:24:00 +0000

Do you need a really quick, clean, powerful diff/merge tool that you can use in windows, mac, and various Unixen? As a happy and pround vim user, I have been enjoying vimdiff for a number of years.

        > gvim -d file1 file2
        > vimdiff file1 file2

(G)vimdiff is wonderful. You can move changes between two versions of a file with great ease (if you know vim) and amazing speed. It can handle files of any size and does a fine job of syncing up both versions.

Vim can do just about anything. I have learned that no matter how much I use and study Vim I still am just scratching the surface of what the editor can do. I find little tricks and configuration options, new keystrokes, and fun little bits of minutae. I think it’s all new. With my memory, sometimes I just think something is new, and have to go check my past notes to see if I already knew it.

Today I (re)learned about diffopt, which makes gvimdiff more wonderful.

    :set diffopt=filler

By default, diffopt is set to “filler”. Filler doesn’t do much, it just adds vertical spaces to keep the text of the left and right pane aligned. It’s a good setting, and I don’t much like working without it. But there are other settings which are overlooked, even by experts.

    : set diffopt+=iwhite

My second favorite is ‘iwhite’, which stands for “ignore whitespace”. It makes gvimdiff ignore leading, trailing, and embedded spaces so that simple acts like retabbing or deleting vertical spaces won’t obscure actual changes. It really helps you to merge changes in situations where you’ve adopted code that was built to entirely different standards.

    :set diffopt+=icase

iCase ignores capitalization, which is not as useful as the other options, since programmers are normally interested in case, but it may be handy when someone has corrected and reformatted SQL. I don’t expect to use it much.

    :set diffopt+=horizontal

The last interesting bit is the choice between vertical splits (the normal case) and horizontal splits (for very long lines on cinema-aspect screens). I hope to never need this option again, but I have needed to deal with absurdly long lines.

If you can use VIM at all, you will find vim’s diffmode to be a very powerful and useful tool. If you can’t use vim already, then maybe vimdiff will be the reason you will learn vim.

Object Mentor Blog: Tag vim

VIM as a Diff/Merge Tool