I am working on a script that has become fairly convoluted. I suspect there are several sections that have nearly identical code. Can I (and how can I) open the file in vim, with two (or more) windows on the buffer, and diff the contents of the windows on the same file? vimdiff seems to work only on two files. If I make a copy of the file and try to vimdiff the two versions, the diff origin remains locked on the beginning of the file. Although I can unscroll-lock the windows, and move the windows to the parts of the file I want to compare the diffs do not show up. Any hints or tips? I could cut and paste the sections I want to compare to different files and then apply vimdiff but then I risk getting lost in what section came from where when I try to patch the separate files together, and I feel sure there must be a more straightforward, easier way.
What I usually do is diff to a copy
:%w %.alt
:vert diffsplit %.alt
And then happiliy rearrange the 'alt' version so that the pseudo-matching bits get aligned.
Note that (presumably) git contains spiffy merge/diff cow-powers that should be able to detect sub-file moved block changes.
Although I haven't (yet) actually put this into practice, I have a hunch that the very nice git plugin fugitive for vim might be able to leverage some of this horsepower to make this easier. Note: fully expect this to require scriptinh before being usable, but I still thought it would be nice to share this idea (perhaps you can share a script if you get to it first!)