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Add util/git-replay-merge.sh
git-replay-merge.sh is a script whose purpose is to make backporting
merge requests more convenient by automating the process as much as
possible.
For more information, including usage examples, see:
https://gitlab.isc.org/isc-projects/bind9/wikis/Backporting-a-Merge-Request
This commit is contained in:
Michał Kępień
210
util/git-replay-merge.sh
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210
util/git-replay-merge.sh
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#!/bin/bash
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#
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# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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#
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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#
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# See the COPYRIGHT file distributed with this work for additional
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# information regarding copyright ownership.
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set -e
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SELF="$(basename $0)"
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SELF="${SELF/-/ }"
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STATE_FILE=".git/REPLAY_MERGE"
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die() {
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for MESSAGE in "$@"; do
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echo -e "${MESSAGE}" >&2
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done
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exit 1
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}
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die_with_usage() {
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die "Usage:" \
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"" \
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" ${SELF} <merge_commit_id> <target_remote> <target_branch>" \
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" ${SELF} --continue" \
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" ${SELF} --abort"
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}
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die_with_continue_instructions() {
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die "" \
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"Replay interrupted. Conflicts need to be fixed manually." \
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"When done, run \"${SELF} --continue\"." \
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"Use \"${SELF} --abort\" to abort the replay."
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}
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die_if_wrong_dir() {
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if [[ ! -d ".git" ]]; then
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die "You need to run this command from the toplevel of the working tree."
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fi
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}
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die_if_not_in_progress() {
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die_if_wrong_dir
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if [[ ! -f "${STATE_FILE}" ]]; then
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die "No replay-merge in progress?"
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fi
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}
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die_if_in_progress() {
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die_if_wrong_dir
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if [[ -f "${STATE_FILE}" ]]; then
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die "Another replay-merge in progress. Use --continue or --abort."
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fi
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}
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die_if_local_behind_target() {
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TARGET_REF_HEAD="$(git rev-list --max-count=1 "${TARGET_REF}")"
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if [[ "$(git merge-base "${TARGET_REF}" "${TARGET_BRANCH}")" != "${TARGET_REF_HEAD}" ]]; then
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die "Local branch ${TARGET_BRANCH} is behind ${TARGET_REF}, cannot merge into it." \
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"Update or remove the local branch, then run \"${SELF} --continue\"." \
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"Use \"${SELF} --abort\" to abort the replay."
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fi
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}
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branch_exists() {
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ESCAPED_BRANCH_NAME=${1//\//\\\/}
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BRANCH_REGEX="/^(remotes\/)?${ESCAPED_BRANCH_NAME}$/"
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if [[ -n "$(git branch -a | awk "\$NF ~ ${BRANCH_REGEX} {print \$NF}")" ]]; then
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return 0
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else
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return 1
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fi
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}
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go() {
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# Process parameters.
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SOURCE_COMMIT="$1"
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TARGET_REMOTE="$2"
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TARGET_BRANCH="$3"
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TARGET_REF="${TARGET_REMOTE}/${TARGET_BRANCH}"
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# Establish the range of commits comprising the source branch.
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REPLAY_COMMIT_RANGE="$(
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git show --format="%P" "${SOURCE_COMMIT}" 2>&1 |
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sed -n "1s/\([0-9a-f]\{40\}\) \([0-9a-f]\{40\}\)/\1..\2/p;"
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)"
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if [[ -z "${REPLAY_COMMIT_RANGE}" ]]; then
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die "${SOURCE_COMMIT} is not a valid merge commit ID."
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fi
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# Extract the name of the source branch.
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SOURCE_BRANCH="$(
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git log --max-count=1 --format="%B" "${SOURCE_COMMIT}" |
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sed -n "s/^Merge branch '\([^'][^']*\).*/\1/p;" |
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head -n 1
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)"
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if [[ -z "${SOURCE_BRANCH}" ]]; then
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die "Unable to extract source branch name from ${SOURCE_COMMIT}."
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fi
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# Ensure the target ref is valid.
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if ! branch_exists "${TARGET_REF}"; then
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die "${TARGET_REF} is not a valid replay target."
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fi
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# Abort if a local branch with the name about to be used for replaying
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# the merge already exists.
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REPLAY_BRANCH="${SOURCE_BRANCH}-${TARGET_BRANCH}"
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if branch_exists "${REPLAY_BRANCH}"; then
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die "Local branch with name ${REPLAY_BRANCH} already exists." \
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"Cannot use it for replaying a merge."
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fi
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# Get the name of the currently checked out branch so that it can be
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# checked out again once the replay is finished.
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CHECKED_OUT_BRANCH="$(git branch | awk "\$1 == \"*\" {print \$2}")"
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# Store state in case it needs to be restored later.
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cat <<-EOF > "${STATE_FILE}"
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CHECKED_OUT_BRANCH="${CHECKED_OUT_BRANCH}"
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SOURCE_COMMIT="${SOURCE_COMMIT}"
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SOURCE_BRANCH="${SOURCE_BRANCH}"
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REPLAY_BRANCH="${REPLAY_BRANCH}"
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TARGET_REMOTE="${TARGET_REMOTE}"
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TARGET_BRANCH="${TARGET_BRANCH}"
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TARGET_REF="${TARGET_REF}"
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EOF
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# Announce the plan.
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echo "Attempting to replay ${REPLAY_COMMIT_RANGE} on top of ${TARGET_REF} in ${REPLAY_BRANCH}..."
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# Switch to the replay branch.
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git checkout -t -b "${REPLAY_BRANCH}" "${TARGET_REF}" >/dev/null
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# Try replaying the branch. If there is any conflict, the command will
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# fail, which means we need to bail and let the user fix the current
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# cherry-pick manually, expecting "git replay-merge --continue" to be
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# used afterwards. If there is no conflict, just proceed with what
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# --continue would do.
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if ! git cherry-pick -x "${REPLAY_COMMIT_RANGE}"; then
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die_with_continue_instructions
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fi
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resume
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}
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resume() {
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# If cherry-picking has not yet been completed, resume it. If it
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# fails, bail. If if succeeds, we can proceed with merging.
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if [[ -f ".git/sequencer/todo" ]]; then
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if ! git cherry-pick --continue; then
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die_with_continue_instructions
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fi
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fi
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# Announce the plan.
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echo "Attempting to merge ${REPLAY_BRANCH} into ${TARGET_BRANCH}..."
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# Check if a local branch with the same name as the target branch
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# exists. If it does not, switch to a new local branch with the same
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# name as the target branch. Otherwise, ensure the local branch is not
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# behind the target branch at the target remote, then switch to it.
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if ! branch_exists "${TARGET_BRANCH}"; then
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git checkout -t -b "${TARGET_BRANCH}" "${TARGET_REF}" >/dev/null
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else
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die_if_local_behind_target
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git checkout "${TARGET_BRANCH}" &>/dev/null
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fi
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# Use the original commit message with a modified subject line.
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COMMIT_MSG="$(
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git log --max-count=1 --format="%B" "${SOURCE_COMMIT}" |
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sed "1s/.*/Merge branch '${REPLAY_BRANCH}' into '${TARGET_BRANCH}'/;"
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)"
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# Merge the replay branch into the local target branch.
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git merge --no-ff -m "${COMMIT_MSG}" "${REPLAY_BRANCH}"
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cat <<-EOF
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Replayed ${SOURCE_BRANCH} onto ${TARGET_BRANCH}.
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To push the replay, use:
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git push ${TARGET_REMOTE} ${TARGET_BRANCH}:${TARGET_BRANCH}
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EOF
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cleanup
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}
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cleanup() {
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# Restore working copy state from before the replay was started,
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# ignoring any potential errors to prevent "set -e" from interfering.
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{
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git merge --abort
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git cherry-pick --abort
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git checkout "${CHECKED_OUT_BRANCH}"
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git branch -D "${REPLAY_BRANCH}"
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} &>/dev/null || true
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rm -f "${STATE_FILE}"
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}
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case "$1" in
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"--abort")
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die_if_not_in_progress
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source "${STATE_FILE}"
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cleanup
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;;
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"--continue")
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die_if_not_in_progress
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source "${STATE_FILE}"
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resume
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;;
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*)
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if [[ $# -ne 3 ]]; then
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die_with_usage
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fi
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die_if_in_progress
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go "$@"
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;;
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esac
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