llvm dev - Jan 2020 - Git autocrlf for Windows - why does the Getting Started guide say to use false?

Hi all,

TL;DR - should we recommend core.autocrlf=input instead of
core.autocrlf=false on Windows?

I recently switched from doing pre-commit builds and tests from my Ubuntu
VM, to my Windows machine where I do all my development. I was aware that
line endings is an issue, so made sure to set core.autocrlf=false as
directed in the Getting Started guide (see
https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm
and https://llvm.org/docs/GettingStarted.html#checkout-llvm-from-git which
explicitly say to use "false"). This seemed a little odd to me, as
that
would mean that if I made any edits, I could potentially end up with
Windows line endings, by my understanding, but I assumed that I had
misunderstood something, so just went along with it.

However, at some point in one of my commits (at least I assume it was one
of mine, since I was working on the file), I somehow managed to change an
existing file to using Windows line endings, which someone else fixed for
me (see commit aca3e70d2bc0dd89b7d486c2a8eac70d8a89e790).

Having double-checked against my settings on my downstream clone, I noticed
that I had core.autocrlf set to input there, and as far as I know, I've
never had any line-ending problems with working with LLVM in that repo. My
understanding is "input" should avoid problems such as mine, i.e. by
ensuring the checked-in files have LF line endings, whilst everybody,
regardless of system will get native line endings in their actual clones. I
am aware that there are some files that deliberately use Windows line
endings - I'm guessing that these are not widespread and that they don't
need regularly modifying, so presumably those users who need to edit those
files can change their setting as needed.

I'm happy to update the docs, but I want to make sure that any update I
make is correct!

James
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The previous discussion about it was here:  https://reviews.llvm.org/D48494

Personally I'd rather see if we could solve it with some clever use of
.gitattributes rather than make it a user-setting but sadly I don't have
time right now to commit to trying out a solution.
I notice that there is one case already of using .gitattributes to make
sure autocrlf doesn't change line endings, FWIW:
https://github.com/llvm/llvm-project/blob/master/llvm/.gitattributes#L19



On Thu, 16 Jan 2020 at 15:19, James Henderson via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> TL;DR - should we recommend core.autocrlf=input instead of
> core.autocrlf=false on Windows?
>
> I recently switched from doing pre-commit builds and tests from my Ubuntu
> VM, to my Windows machine where I do all my development. I was aware that
> line endings is an issue, so made sure to set core.autocrlf=false as
> directed in the Getting Started guide (see
>
https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm
> and https://llvm.org/docs/GettingStarted.html#checkout-llvm-from-git
> which explicitly say to use "false"). This seemed a little odd to
me, as
> that would mean that if I made any edits, I could potentially end up with
> Windows line endings, by my understanding, but I assumed that I had
> misunderstood something, so just went along with it.
>
> However, at some point in one of my commits (at least I assume it was one
> of mine, since I was working on the file), I somehow managed to change an
> existing file to using Windows line endings, which someone else fixed for
> me (see commit aca3e70d2bc0dd89b7d486c2a8eac70d8a89e790).
>
> Having double-checked against my settings on my downstream clone, I
> noticed that I had core.autocrlf set to input there, and as far as I know,
> I've never had any line-ending problems with working with LLVM in that
> repo. My understanding is "input" should avoid problems such as
mine, i.e.
> by ensuring the checked-in files have LF line endings, whilst everybody,
> regardless of system will get native line endings in their actual clones. I
> am aware that there are some files that deliberately use Windows line
> endings - I'm guessing that these are not widespread and that they
don't
> need regularly modifying, so presumably those users who need to edit those
> files can change their setting as needed.
>
> I'm happy to update the docs, but I want to make sure that any update I
> make is correct!
>
> James
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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In general, I think you're asking for trouble if your source control system
is doing anything other than storing the bits you send to it.  It shouldn't
be editing files for you.

There are some places where we specifically want to test that tools behave
correctly with certain line endings, and core.autocrlf=input will break
those tests.  That could probably be solved with proper use of
.gitattributes files, but as Greg mentions, we aren't there yet.

My solution for this in the past has been to use a git extension command
which I call `dos2unix` so that I can run `git dos2unix` and it will run
through my list of staged changes, run dos2unix on all of them, and then I
can `git add -u` the result.  This ensures I'm always committing unix line
endings.

On Thu, Jan 16, 2020 at 7:19 AM James Henderson via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> TL;DR - should we recommend core.autocrlf=input instead of
> core.autocrlf=false on Windows?
>
> I recently switched from doing pre-commit builds and tests from my Ubuntu
> VM, to my Windows machine where I do all my development. I was aware that
> line endings is an issue, so made sure to set core.autocrlf=false as
> directed in the Getting Started guide (see
>
https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm
> and https://llvm.org/docs/GettingStarted.html#checkout-llvm-from-git
> which explicitly say to use "false"). This seemed a little odd to
me, as
> that would mean that if I made any edits, I could potentially end up with
> Windows line endings, by my understanding, but I assumed that I had
> misunderstood something, so just went along with it.
>
> However, at some point in one of my commits (at least I assume it was one
> of mine, since I was working on the file), I somehow managed to change an
> existing file to using Windows line endings, which someone else fixed for
> me (see commit aca3e70d2bc0dd89b7d486c2a8eac70d8a89e790).
>
> Having double-checked against my settings on my downstream clone, I
> noticed that I had core.autocrlf set to input there, and as far as I know,
> I've never had any line-ending problems with working with LLVM in that
> repo. My understanding is "input" should avoid problems such as
mine, i.e.
> by ensuring the checked-in files have LF line endings, whilst everybody,
> regardless of system will get native line endings in their actual clones. I
> am aware that there are some files that deliberately use Windows line
> endings - I'm guessing that these are not widespread and that they
don't
> need regularly modifying, so presumably those users who need to edit those
> files can change their setting as needed.
>
> I'm happy to update the docs, but I want to make sure that any update I
> make is correct!
>
> James
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Right, my understanding is that files that specifically need CRLF should say so
via .gitattributes somewhere.
autocrlf=false ought to work if your Windows editor doesn’t (or can be persuaded
not to) introduce CRLFs.  I’ve observed that the Visual Studio editor will
detect the line-ending style of the file you’re editing, and imitate it.  This
works great until you create a new file. 😝 So I’ve learned to “create” a file by
copying an existing file and then editing it.
I’m inclined to think the llvm.org docs should say to use “input” on Windows,
we’ve been happy with that in the Sony repo as James mentioned.
But I’d also like to hear from a Windows user from outside Sony first.
--paulr

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Greg
Bedwell via llvm-dev
Sent: Thursday, January 16, 2020 12:27 PM
To: jh7370.2008 at my.bristol.ac.uk
Cc: llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] Git autocrlf for Windows - why does the Getting Started
guide say to use false?

The previous discussion about it was here:  https://reviews.llvm.org/D48494

Personally I'd rather see if we could solve it with some clever use of
.gitattributes rather than make it a user-setting but sadly I don't have
time right now to commit to trying out a solution.
I notice that there is one case already of using .gitattributes to make sure
autocrlf doesn't change line endings, FWIW:
https://github.com/llvm/llvm-project/blob/master/llvm/.gitattributes#L19



On Thu, 16 Jan 2020 at 15:19, James Henderson via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Hi all,

TL;DR - should we recommend core.autocrlf=input instead of core.autocrlf=false
on Windows?

I recently switched from doing pre-commit builds and tests from my Ubuntu VM, to
my Windows machine where I do all my development. I was aware that line endings
is an issue, so made sure to set core.autocrlf=false as directed in the Getting
Started guide (see
https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm
and https://llvm.org/docs/GettingStarted.html#checkout-llvm-from-git which
explicitly say to use "false"). This seemed a little odd to me, as
that would mean that if I made any edits, I could potentially end up with
Windows line endings, by my understanding, but I assumed that I had
misunderstood something, so just went along with it.

However, at some point in one of my commits (at least I assume it was one of
mine, since I was working on the file), I somehow managed to change an existing
file to using Windows line endings, which someone else fixed for me (see commit
aca3e70d2bc0dd89b7d486c2a8eac70d8a89e790).

Having double-checked against my settings on my downstream clone, I noticed that
I had core.autocrlf set to input there, and as far as I know, I've never had
any line-ending problems with working with LLVM in that repo. My understanding
is "input" should avoid problems such as mine, i.e. by ensuring the
checked-in files have LF line endings, whilst everybody, regardless of system
will get native line endings in their actual clones. I am aware that there are
some files that deliberately use Windows line endings - I'm guessing that
these are not widespread and that they don't need regularly modifying, so
presumably those users who need to edit those files can change their setting as
needed.

I'm happy to update the docs, but I want to make sure that any update I make
is correct!

James
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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