commit-submodule

#!/bin/sh

# Commit updates to a submodule in the containing repository.
#
# To use this script, make sure any changes to a submodule are
# commited or pulled in the submodule itself and ready to be committed
# to the containing repository. Then run this script (can be done from
# anywhere) and pass the path to the submodule, which generates a commit
# message and commits (just) the submodule.
#
# If changes are needed in the containing repository to accomodate the
# new submodule version, those changes can be amended into the
# generated commit.

SUBMODULE_DIR=$(cd "$1" && pwd)
TOP_DIR=$(cd "${SUBMODULE_DIR}" && git rev-parse --show-superproject-working-tree)
SUBMODULE_NAME=$(realpath --relative-to "${TOP_DIR}" "${SUBMODULE_DIR}")
GIT_DIR="${TOP_DIR}/.git"

HEAD=$(git --git-dir "${TOP_DIR}/.git" rev-parse HEAD:$SUBMODULE_NAME)
WC=$(git --git-dir "${SUBMODULE_DIR}/.git" rev-parse HEAD)

if [ -z "$HEAD" -o -z "$WC" ]; then
  echo "Failed to get submodule info..."
  exit 1
fi

MSG=$(\
	echo "#Note: If changes *are* needed, amend this commit and update the message accordingly." && \
	echo "$SUBMODULE_NAME: Update (no additional changes needed)" && \
	echo && \
	echo "This includes the following commits:" && \
	echo && \
	git --git-dir "${SUBMODULE_DIR}/.git" log --reverse --pretty="format:%h %s" "${HEAD}..${WC}" \
)

cd "${TOP_DIR}" && git commit --edit --message "$MSG" "${SUBMODULE_DIR}"