Q:

Give vimdiff some hints

I've got two c++ files that I want to diff with vimdiff. One of them has a lot more function definitions at the start, before both have a common function that I'm actually interested in. However, vimdiff seems incapable to ignore all the function defs before the common one (perhaps because of different arguments).
Is there any way I can give a hint to vimdiff that, say, line xxx in file1.cxx is equals to line yyy in file2.cxx?
I'm open for alternative solutions without vimdiff, but they must be on linux and very preferably command line, since I'm ssh-ing and any graphical interface is a bit uncomfortable.

A:

Vim just delegates the actual work of comparing the files to the external diff utility, cp. :help diff-diffexpr. The help page also shows how a different utility can be used. Unfortunately, I'm not aware of any more "intelligent" or configurable diff tool that would help in your situation.
A workaround might be (temporarily) removing the excess functions that you're not interested in, anyway. With the BlockDiff plugin, you don't actually need to modify the files. Just select the interesting lines in both windows and execute :[range]BlockDiff on them. Only those sections will then be diffed in a separate tab page. (The plugin mentions this requires a GUI, but Vim in a terminal supports tab pages just as well.)

