How can I view a diff for a single file from a diff file with multiple files?

Question

I have a diff file generated by git diff HEAD~2 > alldiff. Is it possible to view the diff for any one file using alldiff? For example, somecmd alldiff file1withchanges will use alldiff to show changes in file1withchanges in vimdiff.

Answer 1

TIL about this: Is it possible to use vimdiff's side by side view with a regular diff file?

:help diffpatch is your answer.

You just need to say

:diffpatch alldiff

---

Other answer before I knew that^

I'm not normally one to recommend plugins, but I recommend using vim-fugitive. There is a command, :GDiffsplit, that does exactly what you want.

In the buffer you're interested in, simply say :GDiffsplit HEAD~2 and fugitive will do the rest:

• Get git to create the diff
• open a temp buffer with a copy of the file
• Apply the diff
• run :diffthis on the two buffers

Here is me trying to write that as a vimscript function

function! do_the_fugitive_thing(revision)
  " Get git to create the diff
  let my_file = expand("%")
  let my_patch = "/tmp/ari.patch"
  system("git diff ".a:revision." -- ".my_file." > ")

  " open a temp buffer with a copy of the file
  vsp temp_buffer
  set filetype=nofile
  execute "read ".my_file

  " Apply the diff
  system("patch < ".my_patch)
  edit! % " reload buffer after patch application

  " run `:diffthis` on the two buffers
  bufdo diffthis
endfunction

Let me know if this works! Or if you don't know vimscript enough then don't worry about it and just use the plugin...