Re: what file extensions must be explicitly configured with respect to eol-type in gitattributes?

From: Erik Faye-Lund <kusmabite@gmail.com>
Date: Sep 20, 2010, 16:51 UTC
Message-ID: <AANLkTikJO631YDE_UpNrC-4kjc_LF5_Gb8Xv7pCJfOf=@mail.gmail.com>
In-Reply-To: <AANLkTikK2oL3sUYHdqoQ7C47nd6Pi53N17GSfh8nx6Q-@mail.gmail.com>

On Mon, Sep 20, 2010 at 6:19 PM, Robert Buck <buck.robert.j@gmail.com> wrote:

Show 17 quoted lines

> Hello,
>
> One project we have in house has approximately 160 different file
> extensions used for the files checked in. In our repository there are
> files that MUST be CRLF (.bat, .cmd, .vcproj, etc), files that MUST be
> LF (.xml, .xsl, .sh, etc), and files that MUST be binary. All others
> are just text and so long as they appear in native form I'd be happy.
>
> It would seem a default rule to handle text files would make sense:
>
> * text=auto
>
> But I have not found material explaining how git identifies binary
> files, so one concern would be that it could mangle binary file types
> in some cases.
>
> Do I have to explicitly mention all 160 file types in the gitattributes file?

If you want to be 100% sure, yes.

> How does git internally determine whether a file is text vs binary?
> Does it use the 'file' command in Unix?

No. Git applies the following heuristics to the file content:
- Does the file contain any NUL-characters? If so, it's binary.
- Is the ratio of printable characters vs non-printable characters
(when interpreted as ascii) below 128? If so, it's binary.
- Otherwise, it's text.

You can find the exact function here (beware of wrapping): http://git.kernel.org/?p=git/git.git;a=blob;f=convert.c;h=01de9a84c21b31a0120065a32a386f27321cdf7b;hb=HEAD#l77

In general, this works pretty well. In addition, there's the core.safecrlf configuration variable, which can be used to protect you against normalizing the file in such a way that the exact original file can't be recovered.

> And where I am going with this specifically is a question: what rules
> MUST be specifically stated in gitattributes and what rules are there
> implicitly?

Given the above information, you should be able to figure this one out for yourself. The answer depends on how pedantic you are ;)