Monday, March 02, 2015

Autocrlf setting in Git

How autocrlf works:
core.autocrlf=true:    core.autocrlf=input:      core.autocrlf=false:

       repo                     repo                    repo
    /        \               /        \              /        \
crlf->lf    lf->crlf     crlf->lf       \          /            \      
 /              \        /                \      /                \
Reminder: crlf = win-style end-of-line marker, lf = unix-style.
Note that cr (mac-style) in not affected for any of three options above.
When does this warning show up (under Windows)
    - autocrlf = true if you have unix-style lf in one of your files (= RARELY),
    - autocrlf = input if you have win-style crlf in one of your files (= almost ALWAYS),
    - autocrlf = false - NEVER!
What does this warning mean
The warning "LF will be replaced by CRLF" says that you (having autocrlf=true) will lose your unix-style LF after commit-checkout cycle (it will be replaced by windows-style CRLF). Git doesn't expect you to use unix-style LF under windows.
The warning "CRLF will be replaced by LF" says that you (having autocrlf=input) will lose your windows-style CRLF after a commit-checkout cycle (it will be replaced by unix-style LF). Don't use input under windows.
Yet another way to show how autocrlf works
1) true:             x -> LF -> CRLF
2) input:            x -> LF -> LF
3) false:            x -> x -> x
where x is either CRLF (windows-style) or LF (unix-style) and arrows stand for
file to commit -> repository -> checked out file
How to fix
Default value for core.autocrlf is selected during git installation and stored in system-wide gitconfig (%ProgramFiles(x86)%\git\etc\gitconfig). Also there're (cascading in the following order):
   - "global" (per-user) gitconfig located at ~/.gitconfig, yet another
   - "global" (per-user) gitconfig at $XDG_CONFIG_HOME/git/config or $HOME/.config/git/config and
   - "local" (per-repo) gitconfig at .git/config in the working dir.
So, write git config core.autocrlf in the working dir to check the currently used value and
   - add autocrlf=false to system-wide gitconfig             # per-system solution
   - git config --global core.autocrlf false        # per-user solution
   - git config --local core.autocrlf false          # per-project solution
Moral (for Windows):
    - use core.autocrlf = true if you plan to use this project under Unix as well (and unwilling to configure your editor/IDE to use unix line endings),
    - use core.autocrlf = false if you plan to use this project under Windows only,
    - never use core.autocrlf = input unless you have a good reason to (eg if you're using unix utilities under windows or if you run into makefiles issues),
P.S. What to choose when installing git for Windows?
If you're not going to use any of your projects under Unix, don't agree with the default first option. Choose the third one (Checkout as-is, commit as-is). You won't see this message. Ever.
P.P.S. My personal preference is configuring the editor/IDE to use Unix-style endings, and setting core.autocrlf to false.

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