Script to automate maintainance of the ns_system_appearance emacs patch set

sync_emacs_nsappeareance_patches.sh

#!/bin/sh

set -eux

origin_remote="origin"
upstream_remote="upstream"
patch_branch_prefix="ns-system-appearance-change"
emacs_branches="master emacs-30 emacs-29 emacs-28 emacs-27"
gist_ids="9618d4aba60a6e691c3a4bdbefbdb9e9 ba7d50d281e71ba9a585be7c89590b1a 6dbb6f21bbb5756b59c1500f1f97094c 33e099eceae527b368bdf196c95d1ba3 8f430884386d1fcc4e216e484cc44c59"

for command in git gh; do
    if ! command -v "${command}" 1>/dev/null; then
        echo "'${command}' is not in PATH; exiting." >&2
        exit 1
    fi
done

old_pwd="${PWD}"

trap 'cd '"${old_pwd}"'; trap - EXIT; exit' EXIT TERM HUP INT

cd ./emacs

for remote in ${origin_remote} ${upstream_remote}; do
    if ! git ls-remote "${remote}" --exit-code; then
        echo "'${remote}' remote does not exist or is unreachable" >&2
        exit 1
    fi
done

if [ -n "$(git status --porcelain)" ]; then
    echo "working directory is not clean" >&2
    exit 1
fi

i="1"

for branch in ${emacs_branches}; do
    git fetch --quiet "${upstream_remote}" "${branch}"

    behind=$(git rev-list --count "${branch}..${upstream_remote}/${branch}")
    if [ "${behind}" -eq 0 ]; then
        continue
    fi

    git checkout --quiet "${branch}"
    git merge --quiet --ff-only "${upstream_remote}/${branch}"

    if [ "${branch}" = "master" ]; then
        patch_branch="${patch_branch_prefix}"
        gist_name="ns_system_appearance_change.patch"
    else
        patch_branch="${patch_branch_prefix}-${branch}"
        gist_name="ns_system_appearance_change_${branch}.patch"
    fi

    git rebase --quiet "${branch}" "${patch_branch}"
    git push --quiet --no-verify --all --force-with-lease "${origin_remote}"

    gist_id=$(echo "${gist_ids}" | cut -d ' ' -f ${i})
    gist_description="Patch to make emacs (${branch} branch) aware of the macOS 10.14+ system appearance changes."

    gh gist edit "${gist_id}" -f "${gist_name}" -d "${gist_description}" \
        /dev/fd/3 3<<-EOF
			$(git format-patch --stdout HEAD~1)
		EOF

    i=$((i + 1))
done

git checkout --quiet master

Several assumptions are made here;

1. there exists a emacs subdirectory at the script's own path
2. that subdirectory contains the emacs git repository, with two self-explanatory upstream and origin remotes
3. origin is the repo where I maintain the branches, one per patch & major emacs version with a particular naming (see the beginning of the script)
4. emacs-xxx & ns-system-appearance-change(-xxx) branches are already created and pushed to the upstream remote
5. Gists (see gist_ids variable) are already created

The emacs_branches & gist_ids variables should be the only needed updates for a new major emacs release, unless the feature branches cannot be simply rebased.