[Buildroot] [PATCH] support/scripts/apply-patches: use "git apply" as a fallback when applying patches

[Baruch Siach <baruch@tkos.co.il>]

Hi Thomas,

On Thu, Jan 10 2019, Thomas Petazzoni wrote:

> We currently use plain old "patch" to apply patches. While this works
> fine in most situations, it doesn't work well for patches generated
> with git format-patch that:
>
>  - Contain changes to binary files
>
>  - Or contain changes to files in directories that were symlinks to
>    other directories, with the symlink being removed as part of the
>    same patch.
>
> We encountered such issues with a large stack of patches to be applied
> on top of arm-trusted-firmware. Such patches apply perfectly fine with
> "git apply".
>
> Switching everybody to unconditionally use "git apply" seems a bit
> risky, so instead we take a different route: if applying the patch
> with "patch" fails, then we try with "git apply".

This makes git a host dependency. Should we add host-git, or list git
with host requirements?

baruch

> A few implementation notes:
>
>  - The script has "set -e" so for the "patch --dry-run" command, we
>    have to take special precautions to not bail out of the script on
>    error.
>
>  - Also due to "set -e", the check on the return value of "patch" is
>    no longer needed, and we also don't need to check the return value
>    of "git apply".
>
>  - We need to pass "--git-dir=/dev/null", otherwise "git apply"
>    travels up the directory hierarchy until it finds a .git folder. If
>    it finds one, but the files being patched are not under version
>    control, it skips patching those files. Obviously, the files in
>    output/build/foo/ are not under version control, so this behavior
>    is not desirable. Simply making "git apply" believe it is not
>    running from inside a Git repository disables this check.
>
> Cc: Kostya Porotchkin <kostap@marvell.com>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> ---
>  support/scripts/apply-patches.sh | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/support/scripts/apply-patches.sh b/support/scripts/apply-patches.sh
> index 66fef262ee..0fd336968e 100755
> --- a/support/scripts/apply-patches.sh
> +++ b/support/scripts/apply-patches.sh
> @@ -119,11 +119,18 @@ function apply_patch {
>          exit 1
>      fi
>      echo "${path}/${patch}" >> ${builddir}/.applied_patches_list
> -    ${uncomp} "${path}/$patch" | patch -g0 -p1 -E -d "${builddir}" -t -N $silent
> -    if [ $? != 0 ] ; then
> -        echo "Patch failed!  Please fix ${patch}!"
> -        exit 1
> +
> +    # We don't want this to abort the script on failure (script is run
> +    # with set -e)
> +    ${uncomp} "${path}/$patch" | patch -g0 -p1 -E -d "${builddir}" --dry-run -t -N -s && retval=0 || retval=$?
> +    if [ $retval -eq 0 ] ; then
> +	    ${uncomp} "${path}/$patch" | patch -g0 -p1 -E -d "${builddir}" -t -N $silent
> +	    # Due to set -e, if we reach here, applying the patch was successful
> +	    return
>      fi
> +
> +    [ -z "${silent}" ] && gitopts=-v
> +    (cd ${builddir}; ${uncomp} "${path}/$patch" | git --git-dir=/dev/null apply -p1 ${gitopts})
>  }
>
>  function scan_patchdir {


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