The plugin provides a simple command, :Linediff, which is used to diff two separate blocks of text.

A simple example:

def one
  two
end

def two
  three
end

If we mark the first three lines, starting from "def one", in visual mode, and execute the :Linediff command, the signs "1-" will be placed at the start and at the end of the visual mode's range. Doing the same thing on the bottom half of the code, starting from "def two", will result in the signs "2-" placed there. After that, a new tab will be opened with the two blocks of code in vertical splits, diffed against each other.

The two buffers are temporary, but when any one of them is saved, its original buffer is updated. Note that this doesn't save the original buffer, just performs the change. Saving is something you should do later.

Executing the command :LinediffReset will delete the temporary buffers and remove the signs. Executing a new :Linediff will do the same as :LinediffReset, but will also initiate a new diff process.

The statuslines of the two temporary buffers will be changed to contain:

• The original buffer
• The starting line of the selected segment
• The ending line of the selected segment

If you're using a custom statusline and it contains "%f" (the current file's name), that token will simply be substituted by the above data. Otherwise, the entire statusline will be set to a custom one.

If you'd rather the statusline is left untouched, you can set the g:linediff_modify_statusline setting to 0. You can still access the buffer description via b:differ.description.

If you'd like to do some additional setup on the buffers, you can hook into the LinediffBufferReady User autocommand. For instance, in order to stop the linediff with a q, try:

autocmd User LinediffBufferReady nnoremap <buffer> q :LinediffReset<cr>

If you'd like to diff more than two areas of code, you can use the :LinediffAdd command after the first :Linediff to mark more areas. You can then call :LinediffShow to open the diff:

:1,2Linediff
:3,4LinediffAdd
:5,6LinediffAdd
:LinediffShow

This will diff the three specified areas. Alternatively, you can use the :LinediffLast command to add and show the differ. So, the above code is equivalent to:

:1,2Linediff
:3,4LinediffAdd
:5,6LinediffLast

Note that there's a hard limit of 8 diffs set by Vim, so you can't diff more areas than that.

If you have a merge conflict like this one:

def one
<<<<<<< main
  "first"
=======
  "second"
>>>>>>> branch
end

You can easily start a diff between the two variants of the code by executing the :LinediffMerge command. You can use the diffed buffers the same way, or, you can use :LinediffPick to choose one buffer whose contents will replace the entire merge conflict. This also works with three-way diffs:

def one
<<<<<<< master
  "first"
|||||||
  "second"
=======
  "third"
>>>>>>> branch
end

The statuslines of the diff buffers will hold the label of the merge parent for convenience. Also for convenience, executing :LinediffPick directly on the merge area will pick the area without going through the merge buffers first.

Pull requests are welcome, as long as they did not involve LLM usage. Be sure to abide by the CODE_OF_CONDUCT.md as well.