feat: allow hash table with file list for spack cherry-picks

We try to stick to a spack release with selected cherry-picks. Occasionally, spack has a treewide commit that breaks this because all subsequent cherry-picks need the treewide commit to apply successfully, and applying the treewide commit as a cherry-pick would require essentially every commit since the release. This PR adds the ability to apply partial cherry-picks, restricted to just the specified files. This allows is to apply the treewide commit on only the files that need it.

containers/jug/dev.Dockerfile

@@ -41,7 +41,7 @@ git clone --filter=tree:0 https://github.com/${SPACK_ORGREPO}.git ${SPACK_ROOT}
 git -C ${SPACK_ROOT} checkout ${SPACK_VERSION}
 if [ -n "${SPACK_CHERRYPICKS}" ] ; then
   SPACK_CHERRYPICKS=$(git -C ${SPACK_ROOT} rev-list --topo-order ${SPACK_CHERRYPICKS} | grep -m $(echo ${SPACK_CHERRYPICKS} | wc -w)  "${SPACK_CHERRYPICKS}" | tac)
-  eval "declare -A SPACK_CHERRYPICKS_FILES_ARRAY=(${SPACK_CHERRYPICKS})"
+  eval "declare -A SPACK_CHERRYPICKS_FILES_ARRAY=(${SPACK_CHERRYPICKS_FILES})"
   for hash in ${SPACK_CHERRYPICKS} ; do
     if [ -n ${SPACK_CHERRYPICKS_FILES_ARRAY["${hash}"]+found} ] ; then
       git -C ${SPACK_ROOT} show ${hash} -- ${SPACK_CHERRYPICKS_FILES_ARRAY[${hash}]//,/ } | patch -p1 -d ${SPACK_ROOT}