Indent Code and Lists by 4 Spaces in Emacs Markdown Mode

I noticed that my Emacs didn't maintain the current line's indentation when editing code blocks in Markdown (markdown-mode). I indent the first line with 4 spaces like any sane person would. When I hit enter to continue in the next line, thanks to the markdown-mode defaults, I am presented with a new line that's properly indented visually. Only when committing to git did I notice that Emacs inserted tabs instead of spaces. Gasp!

Turns out you're supposed to turn this off for text-mode (a parent mode of Markdown). See the great Emacs indentation tutorial for a good reference.

Using hooks, here's what I am now using to indent by 4 spaces instead of adhering to tab stops:

(add-hook 'text-mode-hook
          '(lambda ()
             (setq indent-tabs-mode nil)
             (setq tab-width 4)))

This will also affect the "press tab to indent the current line" behavior that's active even when your in the middle of text. I needed to get used to this at first, because I expected hitting tab to insert a tabulator at the current cursor position. By default, this indent-line-function is configured to indent the current line up to the previous line's indentation, at least for a lot of cases. In some modes, it is even more aware of the context and does clever things. You can change this to be dump and always indent by 4 spaces, too. Just add this to the hook's lambda list of expressions:

             (setq indent-line-function (quote insert-tab))

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