Running cleanup commands only for edited lines possible?

Question

Referring to clean-up tasks like (but not limited to) the ones detailed in these questions:

• Re-indenting badly indented code

• What's the simplest way to strip trailing whitespace from all lines in a file?

is there a way to apply those commands only the lines of the files which were actually modified? This is for keeping the diff output focused on the actual change after editing source code (a potential code-reviewer would not be confused by the changes involved in cleaning the whole file), while not introducing new formatting problems.

Answer 1

You can use the command folddoopen to execute a command only on the lines that are not within a closed fold.

For example, you can remove whitespace from the end of lines with the command:

:%s/\s\+$//

To apply this only to the lines that are currently not within a closed fold, add folddopen, like this:

:%folddoopen s/\s\+$//

folddoopen can also be abbreviated to foldd.

If you're using Vim as your source control's diff tool, then you can use this to apply edits only to changed lines whilst viewing the diff.

Note that by default, Vim's diff mode displays a few lines before and after each changed section. So in order not to affect lines that are immediately before or after changed lines you'll need to first set context in diffopt to 0 e.g.:

:set diffopt=filler,context:0

For manual edits, you might also find the foldopen option to be useful. It defines which types of commands will cause folds to open. Although note that it does not prevent editing from taking place within the folds in the way that the folddoopen command does.

(If you mean something else by "the lines of the files which were actually modified" then you're going to have to find a way of folding away the unchanged lines before you run the command: the easiest way is to keep an unchanged copy of the file and use vimdiff manually.)