[Mesa-dev] [PATCH] mesa: don't touch git_sha1.h if sha1 didn't change

[Dan Nicholson]

On Sun, May 1, 2011 at 2:53 PM, Marcin Slusarz <marcin.slusarz at gmail.com> wrote:
> Less recompiles...

Good idea. Couple nits.

> ---
>  bin/extract_git_sha1 |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/bin/extract_git_sha1 b/bin/extract_git_sha1
> index e6e6731..fc7bf85 100755
> --- a/bin/extract_git_sha1
> +++ b/bin/extract_git_sha1
> @@ -1,10 +1,14 @@
>  #!/bin/sh
> -touch src/mesa/main/git_sha1.h

Instead of moving the touch out to when there's no git, perhaps it
would be better to just touch the file when it doesn't exist.

[ -f src/mesa/main/git_sha1.h ] || touch src/mesa/main/git_sha1.h

That way your later diff command won't complain on stdout that one of
the files is missing on a fresh checkout.

>  if which git > /dev/null; then
>     # Extract the 7-digit "short" SHA1 for the current HEAD, convert
>     # it to a string, and wrap it in a #define.  This is used in
>     # src/mesa/main/version.c to put the GIT SHA1 in the GL_VERSION string.
>     git log -n 1 --oneline |\
>        sed 's/^\([^ ]*\) .*/#define MESA_GIT_SHA1 "git-\1"/' \
> -       > src/mesa/main/git_sha1.h
> +       > src/mesa/main/git_sha1.h.tmp
> +    if ! diff src/mesa/main/git_sha1.h.tmp src/mesa/main/git_sha1.h >/dev/null; then
> +       mv src/mesa/main/git_sha1.h.tmp src/mesa/main/git_sha1.h
> +    fi

I might suggest using "cmp -s" here since it's more suited to what we
want: just says if the files are the same without having to figure out
what's different.

> +else
> +    touch src/mesa/main/git_sha1.h
>  fi

--
Dan