Remove unecessary indents while keeping the relative indentation

Question

I am looking for a transformation that would change this text:

    text
        indented
        text
            double
            indented
            text
        indented
        again

to:

text
    indented
    text
        double
        indented
        text
    indented
    again

But then wouldn't change anything if applied again.

I a nutshell, I need to keep the minimal indentation level without loosing the relative indentations of the lines. So just drop the indentations that run all along the selection.

Is there a clever way to do so ?

Answer 1

Delete the text linewise and then paste with ]p with your cursor from an empty line.

dG]p

Here ]p is doing all the hard work. ]p will paste the text, but will adjust the indent to the current line.

For more help see:

:h ]p

Answer 2

The following code add a mapping <leader>s that should do what you want on the specific file you provided, if you use spaces to indent.

nnoremap <leader>s :<c-u>call UnindentSpaces()<cr>

function! UnindentSpaces()

    function! GlobalUnindent()

        let line = getline('.')
        let p = match(line, '\S') - s:n
        s;^\s*;\=repeat(' ', p);

    endfunction

    let line = getline(1)
    let s:n = match(line, '\S')
    if s:n > 0
        g/^/call GlobalUnindent()
    endif

endfunction

Conditions in which I tested this code :

set expandtab
set tabstop=4 softtabstop=4 shiftwidth=4

If you use a tab character to indent, then the following code should be used instead (<leader>t) :

nnoremap <leader>t :<c-u>call UnindentTabs()<cr>

function! UnindentTabs()

    function! GlobalUnindent()

        let line = getline('.')
        let p = match(line, '\S') - s:n
        s;^\s*;\=repeat("\t", p);

    endfunction

    let line = getline(1)
    let s:n = match(line, '\S')
    if s:n > 0
        g/^/call GlobalUnindent()
    endif

endfunction

Conditions in which I tested this code :

set noexpandtab
set tabstop=4 softtabstop=4 shiftwidth=4

Tell me if it works for you, otherwise I'll try to modify it if I can.

---

Edit : if you can rely on the first character of the first line to detect whether the file use spaces or tabs for indentation, then I think you can do it with only one mapping (<leader>u) and one function which will cover both cases (tabs vs spaces) :

nnoremap <leader>u :<c-u>call Unindent()<cr>

function! Unindent()

    function! GlobalUnindent()

        let line = getline('.')
        let p = match(line, '\S') - s:n
        s;^\s*;\=repeat(s:indentchar, p);

    endfunction

    let line = getline(1)
    let s:indentchar = matchstr(line, '\%1c.')
    let s:n = match(line, '\S')

    if s:n > 0
        g/^/call GlobalUnindent()
    endif

endfunction