add-commit-pr-id

#!/usr/bin/env bash
#
# Copyright (C) 2026  Vates SAS
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

# ==============================================================================
# Make the title of every commit of the current branch end with ` (#<pr-number>)`.
# Commits whose title already ends with this ID only are left untouched, so the script can be run
# several times.
#
# Usage: add-commit-pr-id [--force] <base-sha> <head-sha> <pr-number>
#
# - `<base-sha>`: base of the pull request to check and modify.
# - `<head-sha>`: head of the pull request to check and modify.
# - `<pr-number>`: number of the pull request.
# - `--force`: replace the existing pull request IDs of the titles.
#
# Every trailing ` (#<digits>)` of a title is considered to be a pull request ID. Without `--force`,
# the commits that already end with another ID are ignored (and listed), the others are rewritten:
# an ignored commit is probably in the range because the base is wrong, or the range contains
# commits of other pull requests.
# ==============================================================================

set -euo pipefail

SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
readonly SCRIPT_DIR

readonly AMEND_SCRIPT_PATH="${SCRIPT_DIR}/amend-commit-pr-id"

source "${SCRIPT_DIR}/lib/git.sh"
source "${SCRIPT_DIR}/lib/pr-id.sh"

# ==============================================================================

readonly FORCE_OPTION="--force"

FORCE=false
ARGS=()
for arg in "$@"; do
    if [ "$arg" = "$FORCE_OPTION" ]; then
        FORCE=true
    else
        ARGS+=("$arg")
    fi
done
readonly FORCE
readonly ARGS

if [ "${#ARGS[@]}" -ne 3 ]; then
    echo "Usage: $0 [${FORCE_OPTION}] <base-sha> <head-sha> <pr-number>" >&2
    exit 2
fi

BASE_SHA=$(resolve_commit "${ARGS[0]}")
readonly BASE_SHA

HEAD_SHA=$(resolve_commit "${ARGS[1]}")
readonly HEAD_SHA

readonly PR_NUMBER=${ARGS[2]}
if ! is_pr_number "$PR_NUMBER"; then
    echo "Invalid pull request number: \`${PR_NUMBER}\`." >&2
    exit 2
fi

# ------------------------------------------------------------------------------

if ! git diff --quiet || ! git diff --cached --quiet; then
    echo "The working tree has uncommitted changes: commit or stash them first." >&2
    exit 1
fi

if [ "$(git rev-parse HEAD)" != "$HEAD_SHA" ]; then
    echo "\`HEAD\` is not \`${HEAD_SHA}\`: checkout the head of the pull request first." >&2
    exit 1
fi

# ------------------------------------------------------------------------------

if ! MERGE_BASE_SHA=$(git merge-base "$BASE_SHA" "$HEAD_SHA"); then
    echo "No common ancestor between \`${BASE_SHA}\` and \`${HEAD_SHA}\`." >&2
    exit 2
fi
readonly MERGE_BASE_SHA

readonly COMMIT_RANGE="${MERGE_BASE_SHA}..${HEAD_SHA}"
if [ -n "$(git rev-list --merges "${MERGE_BASE_SHA}..${HEAD_SHA}")" ]; then
    echo "Merge commits found in \`${COMMIT_RANGE}\`: this script only supports linear history." >&2
    exit 1
fi

mapfile -t hashes < <(git log --format=%H "${MERGE_BASE_SHA}..${HEAD_SHA}")

# ------------------------------------------------------------------------------

PR_ID_SUFFIX=$(get_pr_id_suffix "$PR_NUMBER")
readonly PR_ID_SUFFIX

to_rewrite=0
to_ignore=0
for hash in "${hashes[@]}"; do
    subject=$(git log -1 --format=%s "$hash")
    if [ "$(with_pr_id "$subject" "$PR_ID_SUFFIX")" = "$subject" ]; then
        continue
    fi

    # The title already ends with a pull request ID other than the requested one.
    if has_pr_id "$subject" && ! $FORCE; then
        to_ignore=$((to_ignore + 1))
        echo "Commit ${hash} ignored, it already has another pull request ID: \"${subject}\"." >&2
        continue
    fi

    to_rewrite=$((to_rewrite + 1))
done

if [ "$to_rewrite" -eq 0 ]; then
    if [ "$to_ignore" -eq 0 ]; then
        echo "Nothing to do: every commit of \`${COMMIT_RANGE}\` already ends with \"${PR_ID_SUFFIX}\"."
    else
        echo "Nothing to do: ${to_ignore} commit(s) of \`${COMMIT_RANGE}\` ignored with another pull request ID, the others already end with \"${PR_ID_SUFFIX}\"."
    fi
    exit 0
fi

# ------------------------------------------------------------------------------

exec_options=()
if $FORCE; then
    exec_options+=("$FORCE_OPTION")
fi

readonly PREVIOUS_HEAD=$HEAD_SHA
printf -v EXEC_COMMAND '%q ' "$AMEND_SCRIPT_PATH" "${exec_options[@]}" "$PR_ID_SUFFIX"
readonly EXEC_COMMAND

if ! rebase_output=$(GIT_SEQUENCE_EDITOR=: git rebase --interactive --no-autosquash --exec "$EXEC_COMMAND" "$MERGE_BASE_SHA" 2>&1); then
    echo "$rebase_output" >&2
    git rebase --abort || true
    echo "Rewrite failed, branch restored (previous HEAD: ${PREVIOUS_HEAD})." >&2
    exit 1
fi

echo "${to_rewrite} commit title(s) updated with \"${PR_ID_SUFFIX}\" (previous HEAD: ${PREVIOUS_HEAD})."
if [ "$to_ignore" -ne 0 ]; then
    echo "${to_ignore} commit(s) ignored because they already have another pull request ID."
fi