linux-kernel - Re: [PATCH] .gitattributes: set diff driver for Rust source code files

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Message-ID: <20230419131121.6f5f5acf.gary@garyguo.net>
Date:   Wed, 19 Apr 2023 13:11:21 +0100
From:   Gary Guo <gary@...yguo.net>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Wedson Almeida Filho <wedsonaf@...il.com>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Jean Delvare <jdelvare@...e.de>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH] .gitattributes: set diff driver for Rust source code
 files

On Wed, 19 Apr 2023 01:30:48 +0200
Miguel Ojeda <ojeda@...nel.org> wrote:

> Git supports a builtin Rust diff driver [1] since v2.23.0 (2019).
> 
> It improves the choice of hunk headers in some cases, such as
> diffs within methods, since those are indented in Rust within
> an `impl` block, and therefore the default diff driver would
> pick the outer `impl` block instead (rather than the method
> where the changed code is).
> 
> For instance, with the default diff driver:
> 
>     @@ -455,6 +455,8 @@ impl fmt::Write for RawFormatter {
>              // Amount that we can copy. `saturating_sub` ensures we get 0 if `pos` goes past `end`.
>              let len_to_copy = core::cmp::min(pos_new, self.end).saturating_sub(self.pos);
> 
>     +        test_diff_driver();
>     +
>              if len_to_copy > 0 {
>                  // SAFETY: If `len_to_copy` is non-zero, then we know `pos` has not gone past `end`
>                  // yet, so it is valid for write per the type invariants.
> 
> With the Rust diff driver:
> 
>     @@ -455,6 +455,8 @@ fn write_str(&mut self, s: &str) -> fmt::Result {
>              // Amount that we can copy. `saturating_sub` ensures we get 0 if `pos` goes past `end`.
>              let len_to_copy = core::cmp::min(pos_new, self.end).saturating_sub(self.pos);
> 
>     +        test_diff_driver();
>     +
>              if len_to_copy > 0 {
>                  // SAFETY: If `len_to_copy` is non-zero, then we know `pos` has not gone past `end`
>                  // yet, so it is valid for write per the type invariants.
> 
> Thus set the `rust` diff driver for `*.rs` source files.
> 
> Link: https://git-scm.com/docs/gitattributes#_defining_a_custom_hunk_header [1]
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>

This is also done in rustc repo:
https://github.com/rust-lang/rust/blob/master/.gitattributes

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
>  .gitattributes | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/.gitattributes b/.gitattributes
> index c9ba5bfc4036..2325c529e185 100644
> --- a/.gitattributes
> +++ b/.gitattributes
> @@ -2,3 +2,4 @@
>  *.[ch] diff=cpp
>  *.dts diff=dts
>  *.dts[io] diff=dts
> +*.rs diff=rust
> 
> base-commit: 09a9639e56c01c7a00d6c0ca63f4c7c41abe075d