Re: [edk2-devel] [PATCH v2] BaseTools/Conf/gitattributes: fix "--function-context" for C source code

["Leif Lindholm" <leif@nuviainc.com>]

On Mon, Jan 20, 2020 at 10:42:45 +0100, Laszlo Ersek wrote:
> The "--function-context" ("-W") option of git-diff displays the entire
> body of a modified function, not just small modified hunks within the
> function. It is useful for reviewers when the code changes to the function
> are small, but they could affect, or depend on, control flow that is far
> away in the same function.
> 
> Of course, the size of the displayed context can be controlled with the
> "-U" option anyway, but such fixed-size contexts are usually either too
> small, or too large, in the above scenario.
> 
> It turns out that "--function-context" does not work correctly for C
> source files in edk2. In particular, labels for the goto instruction
> (which the edk2 coding style places in the leftmost column) appear to
> terminate "--function-context".
> 
> The "git" utility contains built-in hunk header patterns for the C and C++
> languages. However, they do not take effect in edk2 because we don't
> explicitly assign the "cpp" git-diff driver to our C files. The
> gitattributes(5) manual explains that this is required:
> 
> >            There are a few built-in patterns to make this easier, and
> >            tex is one of them, so you do not have to write the above in
> >            your configuration file (you still need to enable this with
> >            the attribute mechanism, via .gitattributes). The following
> >            built in patterns are available:
> >
> >            [...]
> >
> >            *   cpp suitable for source code in the C and C++
> >                languages.
> 
> The key statement is the one in parentheses.
> 
> Grab the suffix lists from the [C-Code-File] and [Acpi-Table-Code-File]
> sections of "BaseTools/Conf/build_rule.template", add "*.h" and "*.H", and
> mark those as belonging to the "cpp" git-diff driver.
> 
> This change has a dramatic effect on the following command, for example:
> 
> $ git show -W 2ef0c27cb84c
> 
> Cc: Bob Feng <bob.c.feng@intel.com>
> Cc: Leif Lindholm <leif.lindholm@linaro.org>
> Cc: Liming Gao <liming.gao@intel.com>
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Leif Lindholm <leif@nuviainc.com>
also
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
(if it jars too much to use a different one from Cc: tag above)

For other purposes, the Linaro address can now be considered retired.

/
    Leif

> ---
> 
> Notes:
>     v2:
>     
>     - take suffixes from "BaseTools/Conf/build_rule.template" [Leif]
>     
>     - replace "*.h" / "*.c" in the commit message with "C source" and
>       [C-Code-File] / [Acpi-Table-Code-File]
>     
>     - Supersedes: <20200116184929.18020-1-lersek@redhat.com>
>       http://mid.mail-archive.com/20200116184929.18020-1-lersek@redhat.com
>       https://edk2.groups.io/g/devel/message/53312
> 
>  BaseTools/Conf/gitattributes | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/BaseTools/Conf/gitattributes b/BaseTools/Conf/gitattributes
> index 58b93e9d4c27..319e89064133 100644
> --- a/BaseTools/Conf/gitattributes
> +++ b/BaseTools/Conf/gitattributes
> @@ -17,3 +17,14 @@
>  *.fdf     diff=ini
>  *.fdf.inc diff=ini
>  *.inf     diff=ini
> +*.c       diff=cpp
> +*.C       diff=cpp
> +*.cc      diff=cpp
> +*.CC      diff=cpp
> +*.cpp     diff=cpp
> +*.Cpp     diff=cpp
> +*.CPP     diff=cpp
> +*.aslc    diff=cpp
> +*.act     diff=cpp
> +*.h       diff=cpp
> +*.H       diff=cpp
> -- 
> 2.19.1.3.g30247aa5d201
> 
> 
> 
>