Update an s3-based Yum repo with a new package with minimal data transfer

updaterepo.sh

#!/bin/bash -x

# Using s3 to host a yum repo has many advantages, but there is often
#   a need to push new artifacts and update the metadata.  To achieve
#   this, we will mirror the s3 repo locally in a crafty way.  We will 
#   grab the full repo metadata (in the repodata directory), but the packages
#   will not be downloaded. Instead, the files will be created but will be
#   EMPTY. This avoids large data sync's.

OPTIND=1
RPM_FILE=""
LOCAL_REPO=~/localrepo
REMOTE_REPO=s3://my-repo

while getopts "f:" opt; do
    case "$opt" in
    f)  RPM_FILE=$OPTARG
        ;;
    esac
done
shift $((OPTIND-1))
[ "$1" = "--" ] && shift

# get the architecture from the rpm file
ARCH=`rpm -qp --queryformat '%{ARCH}' $RPM_FILE`

mkdir -p $LOCAL_REPO

# sycn the repodata
aws s3 sync --exclude='*' --include 'repodata/*' $REMOTE_REPO $LOCAL_REPO

# sync the package files by name only, the files will be EMPTY
aws s3 sync --dryrun --exclude 'repodata/*' $REMOTE_REPO $LOCAL_REPO  | perl -pe 's/^.* to //' | xargs -I{} install -D <(cat /dev/null) {}

# add the new package
cp --preserve $RPM_FILE $LOCAL_REPO/$ARCH/

# update the metadata. --skip-stat is needed because the package files from s3 are EMPTY
createrepo --verbose --skip-stat --update $LOCAL_REPO

# remove the EMPTY files
find $LOCAL_REPO -type f -size 0 -print0 | xargs -0 rm

# sync the changes to s3. The repodata file names are changed by createrepo, so we need to use the --delete flag
aws s3 sync --delete $LOCAL_REPO/repodata/ $REMOTE_REPO/repodata/
aws s3 sync $LOCAL_REPO $REMOTE_REPO