v2Switch grep from non-portable BRE to portable ERE

> ---
>  mergetools/vimdiff           | 2 +-
>  t/t1404-update-ref-errors.sh | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mergetools/vimdiff b/mergetools/vimdiff
> index 734d15a03b..f8ad6b35d4 100644
> --- a/mergetools/vimdiff
> +++ b/mergetools/vimdiff
> @@ -325,7 +325,7 @@ gen_cmd () {
>  		fi
>  
>  		# If this is a single window diff with all the buffers
> -		if ! echo "$tab" | grep ",\|/" >/dev/null
> +		if ! echo "$tab" | grep -E ",|/" >/dev/null
>  		then
>  			CMD="$CMD | silent execute 'bufdo diffthis'"
>  		fi
> diff --git a/t/t1404-update-ref-errors.sh b/t/t1404-update-ref-errors.sh
> index 98e9158bd2..67ebd81a4c 100755
> --- a/t/t1404-update-ref-errors.sh
> +++ b/t/t1404-update-ref-errors.sh
> @@ -100,7 +100,7 @@ df_test() {
>  		printf "%s\n" "delete $delname" "create $addname $D"
>  	fi >commands &&
>  	test_must_fail git update-ref --stdin <commands 2>output.err &&
> -	grep "fatal:\( cannot lock ref $SQ$addname$SQ:\)\? $SQ$delref$SQ exists; cannot create $SQ$addref$SQ" output.err &&
> +	grep -E "fatal:( cannot lock ref $SQ$addname$SQ:)? $SQ$delref$SQ exists; cannot create $SQ$addref$SQ" output.err &&
>  	printf "%s\n" "$C $delref" >expected-refs &&
>  	git for-each-ref --format="%(objectname) %(refname)" $prefix/r >actual-refs &&
>  	test_cmp expected-refs actual-refs
> 

> On Fri, May 17, 2024 at 09:01:49PM +0200, Marcel Telka wrote:
> > This makes the grep usage fully POSIX compliant.  The ability to
> 
> Nit: we typically don't say "This commit", of which "This" is another
> version. Instead, we use imperative style as if instructing the code to
> change. Also, we typically first explain what the problem is before we
> say how we fix it.
> 
> I don't think this is worth a reroll though, it's only a hint for the
> next patch you may be sending :)
> 
> > enable ERE features in BRE using backslash is a GNU extension.
> > 
> > Signed-off-by: Marcel Telka <marcel@telka.sk>
> 
> It would have been nice if this thread was connected to the thread of
> your first version so that it's easier to follow the discussion, e.g. by
> using `--in-reply-to=` in git-send-email(1) or git-format-patch(1).