[Buildroot] [PATCH] Restrict tar transform to regular files Without this

[Yann E. MORIN <yann.morin.1998@free.fr>]

Timothy, All,

On 2019-04-26 11:49 -0500, Timothy Pearson spake thusly:
>  restriction, symlinks are rewritten and corrupted.

Something is amiss in your commit log. It shoul;d be:

    titile on a single line

    Some text on
    multiple lines.

    Signed-off-by: Your NAME <your@email>

> Example without the restriction:
> 
> Input tree (valid):
> package-githash/file1
> package-githash/link -> ./file1
> 
> Output tree (broken):
> package-githash/file1
> package-githash/link -> package-githash/file1
> ---
>  support/download/git | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/support/download/git b/support/download/git
> index 17ca04eb98..1acb795c81 100755
> --- a/support/download/git
> +++ b/support/download/git
> @@ -190,7 +190,7 @@ LC_ALL=C sort <"${output}.list" >"${output}.list.sorted"
>  
>  # Create GNU-format tarballs, since that's the format of the tarballs on
>  # sources.buildroot.org and used in the *.hash files
> -tar cf - --transform="s#^\./#${basename}/#" \
> +tar cf - --transform="flags=r;s#^\./#${basename}/#" \

OK, so this is a nice trick and all, but I can't find any reference to
it in the man page. But I see it's in the git tree in doc/tar.texi...

Your proposal would exclude hardlinks too, which is not correct I think.
In fact, we would need to use 'S' (upper-case 'S') here, because we want
it to apply to anything but symlinks.

Also, the texi file states that "Default scope flags can also be changed
using flags= statement in the transform expression." However, they are
standard flags too, quoting:

    Supported flags are:
        g [...]
        i [...]
        x [...]
        <number> [...]

    [...]

    In addition, several transformation scope flags are supported, that
    control to what files transformations apply.  These are:
        r   Apply transformation to regular archive members.
        R   Do not apply transformation to regular archive members.
        s   Apply transformation to symbolic link targets.
        S   Do not apply transformation to symbolic link targets.
        h   Apply transformation to hard link targets.
        H   Do not apply transformation to hard link targets.

So I think we could simply write:

    --transform="s#^\./#${basename}/#S'

Regards,
Yann E. MORIN.

>           --numeric-owner --owner=0 --group=0 --mtime="${date}" --format=gnu \
>           -T "${output}.list.sorted" >"${output}.tar"
>  gzip -6 -n <"${output}.tar" >"${output}"
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