Re: [PATCH 3/6] GIT-VERSION-GEN: Use sed instead of expr

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 5, 2019, 22:37 UTC
Message-ID: <xmqqy307kzn3.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <df67a7e1d307d6a7a91ae1bba085959154006ed1.1564876327.git.gitgitgadget@gmail.com>

"lufia via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 19 quoted lines

> From: lufia <lufia@lufia.org>
>
> Plan 9 don't have expr(1).
>
> Signed-off-by: lufia <lufia@lufia.org>
> ---
>  GIT-VERSION-GEN | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
> index a0766f64ed..754d4486f5 100755
> --- a/GIT-VERSION-GEN
> +++ b/GIT-VERSION-GEN
> @@ -26,7 +26,7 @@ else
>  	VN="$DEF_VER"
>  fi
>  
> -VN=$(expr "$VN" : v*'\(.*\)')
> +VN=$(echo "$VN" | sed 's/^v*//')

The expr utility is often a shell built-in, but sed is almost never (as it is a lot more heavy-weight command). It may not be a bad idea to get rid of expr with a simple shell parameter expansion, e.g.

	VN=${VN#v}

instead.

The original explicitly is prepared to see no 'v' at the beginning (in which case it just passes VN intact), or more than one 'v's (in which case all leading 'v's are stripped), while the shell parameter expansion strips zero or one 'v' at the beginning. So there is a slight "regression" there, but I do not think it matters (certainly, it was *NOT* my intention while writing the original to strip two or more 'v's). 181129d2 ("For release tarballs, include the proper version", 2006-01-09) snuck in the "all leading 'v's are stripped" without sufficient explanation, but I do not think it was an attempt to allow two or more 'v's.