Skip undo step in Vim

Question

Let's say I'm at state A in my document. I then make changes B, C, and D (in order).

Is there a way I can keep changes B and D, but skip C?

Or, let's say I'm at state A in my document. I make change B, undo it, and then make changes C and D (so Vim has an undo tree with two branches). I then change my mind and decide I want to use B and D but not C.

How can I do this in Vim? I have the gundo.vim plugin installed, but I haven't used it that much.

Answer 1

Well, I'll take a stab at this and say: No, I don't think there's a way to do exactly what you want with vim.

gundo.vim adds a nice interface to vim's undo, but doesn't change its core capabilities. So I took a look at the official vim docs to see if there's any hints to whether it is capable of this:

• vim docs: undo
• User manual page about undo

Nothing about merging two branches together. I think ewh and ZyX are right: to get a general solution for merging B with D, vim would need either for

1. Bram to add it as a separate feature in a future version
2. someone to implement it in a plugin by integrating with something that can already do merges (like git/hg)

You can of course try to do it manually by having files with versions B, C and D as well as a few diffs open.

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Note: If I misunderstood and you weren't wondering about a general solution and are looking for help with a specific instance of this, let me know and I'll see what I can do :)

Answer 2

Is there a way I can keep changes B and D, but skip C?

You're at state D. :w file.ext_D

Backtrack to state C. :w file_ext_C

Backtrack to state B. :w file.ext_B

:!kdiff3 file.ext_B file.ext_C file.ext_D

This gives a 3 way merge of the differences, but still you'd have to manually go in and choose every red line in D for each merge conflict. Not exactly an easy solution.

If instead you do

:!kdiff3 file.ext_C file.ext_B file.ext_D

Then the merge happens automatically (except for individual lines with multiple changes)

For more complicated scenarios it gets tougher.

Note: I'm not sure how a revision control tool is much help. You're basically doing something like creating a patch between B and D, and then subtracting the patch from C to D from it. It seems to me that revision control systems are usually designed to manage merges between different sources of changes, not changes along a single branch.

kdiff3 is available at: http://kdiff3.sourceforge.net/