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+---
+layout: post
+title: Don't blindly remove trailing white spaces
+summary: In which I explain why removing blindly white spaces is harmful
+---
+
+I don't like trailing white spaces in my source code. I've configured my editors to highlight them
+so I don't add them by accident, and when possible, I remove them. But it doesn't mean that all of
+them should be removed blindly.
+
+In this post, I'm talking about files that are managed by a SCM. When working on such a text file,
+editor's hooks that delete them when writing a file can be more annoying than keeping them in place.
+A change should only touch lines that are relevant to the fix or feature beeing added. Touching
+lines that are not relevant are creating noise in the history. I've made this mistake in the past,
+and I've learned my lessons.
+
+## Pain for the reviewer
+
+The person who will review the change will have to make an extra effort to understand why the diff
+highlight some lines where it looks like there's no change. It's a distraction to his main task, and
+it doesn't bring any benefit to the change beeing submitted.
+
+## Pain for the person browsing the history
+
+When someone browse the history and try to understand what changed between two versions, the
+deletion is just noise. It's already hard to make the mental effort to read a diff, and understand
+what and why things have changed. Adding some extra noise is annoying.
+
+Running a tool like `git blame` shows how useless this is, for both the person reading the history
+and the author.
+
+## Tips
+
+Configure your editor to highlight them. If you are using Emacs, you can do it with
+
+```
+(require 'whitespace)
+(global-whitespace-mode 1)
+(setq whitespace-style '(face trailing tabs tab-mark))
+```
+
+With vim, you can add the following:
+
+```
+set list lcs=trail:·,tab:»·
+highlight ExtraWhitespace ctermbg=red guibg=red
+```
+
+It's also possible to configure `git` to highlight them when running `git add -p`, by running
+
+```
+git config --global core.whitespace trailing-space,space-before-tab
+```
+
+`git` will complain if it finds white spaces in your change, so you have time to fix and remove
+them.
+
+If you really don't want any trailing white spaces, you can also configure your SCM with a
+post-commit hook to reject commits that contains them.
+
+If you're using `vimdiff` to read a diff, it's possible to not highlight white spaces with `set
+diffopt+=iwhite`. This can makes it a little bit easier to read messy diff.