Re: [PATCH v2] meson: disable coccinelle configuration when building from a tarball

> Wiring up coccinelle in the build, depends on running git commands to
> get the list of files to operate on. Reasonable, for a feature mainly
> used by people developing on git. If building git itself from a tarball
> distribution of git's own source code, one likely does not need to run
> coccinelle.
> 
> But running those git commands failed, and caused the build to error
> out, if `spatch` was installed -- because the build assumed that its
> presence indicated a desire to use it on this source tree. Instead, we
> can expand the conditional to check for both `spatch` and the `.git`
> file or directory.
> 
> Meson's `opt.require()` method allows us to add a prerequisite for the
> feature option. If the prerequisite fails, then the option either:
> 
> - converts autodetection to disabled
> 
> - emits an informative error if the feature was set to enabled:
>   ```
>   ERROR: Feature coccinelle cannot be enabled: coccinelle can only be run from a git checkout
>   ```

> Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>
> ---
> 
> v2: accidentally chopped off part of the commit message, sorry...
> 
>  contrib/coccinelle/meson.build | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/contrib/coccinelle/meson.build b/contrib/coccinelle/meson.build
> index 5d76a7fee6..ea054c924f 100644
> --- a/contrib/coccinelle/meson.build
> +++ b/contrib/coccinelle/meson.build
> @@ -1,4 +1,9 @@
> -spatch = find_program('spatch', required: get_option('coccinelle'))
> +coccinelle_opt = get_option('coccinelle').require(
> +  fs.exists(meson.project_source_root() / '.git'),
> +  error_message: 'coccinelle can only be run from a git checkout',
> +)
> +
> +spatch = find_program('spatch', required: coccinelle_opt)
>  if not spatch.found()
>    subdir_done()
>  endif
> 
> base-commit: c1d6628c9433c09ff62f916f2b933ee12995e9d8