124 lines
4.0 KiB
Bash
Executable File
124 lines
4.0 KiB
Bash
Executable File
#!/usr/bin/env bash
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set -eou pipefail
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help() {
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cat <<EOT
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$0: Prepare a pull request that syncs a branch with upstream
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Usage:
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$0 [--switch] <base-branch> <upstream-ref>
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This script creates a sync local branch pointing to <upstream-ref>. Moreover, it
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generates a helper script for opening a pull request (PR) merging the created
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local branch into <base-branch>.
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The synced upstream PRs are listed in the title and the description of the PR.
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(This relies on upstream merging PRs using merge commits with titles of the form
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"Merge <repo>#<prnum>: ...".)
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Arguments:
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--switch: Try to switch to the created sync branch
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<base-branch>: The branch to sync with upstream
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<upstream-ref>: The upstream ref to merge into <base-branch>
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Usage examples:
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$0 --switch master upstream/master
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$0 master abc1234
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To find candidate merge commits from <upstream-ref> (oldest first), use:
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git log --oneline --topo-order --reverse --merges \$(git merge-base <upstream-ref> <base-branch>)..<upstream-ref>
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EOT
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}
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### Parse arguments
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SWITCH=false
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if [ "$#" -ge 1 ] && [ "$1" = "--switch" ]; then
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SWITCH=true
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shift
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fi
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if [ "$#" -ne 2 ]; then
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help
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exit 1
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fi
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BASE_BRANCH="$1"
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UPSTREAM_REF="$2"
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### Create PR metadata
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TITLE="Upstream PRs"
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RANGESTART_COMMIT=$(git merge-base "$UPSTREAM_REF" "$BASE_BRANCH")
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RANGEEND_COMMIT=$(git rev-parse "$UPSTREAM_REF")
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COMMITS=$(git --no-pager log --pretty=format:%H --topo-order --reverse --merges "$RANGESTART_COMMIT".."$RANGEEND_COMMIT")
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# If there are no commits, exit successfully
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if [ -z "$COMMITS" ]; then
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echo "No merge commits in range ${RANGESTART_COMMIT}..${RANGEEND_COMMIT}" >&2
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exit 0
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fi
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BODY="${GITHUB_ACTIONS+*Note: This PR has been created by a GitHub Actions workflow without human involvement.*
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}"
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BODY+="This PR syncs the following upstream PRs:"
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for COMMIT in $COMMITS; do
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PRNUM=$(git log -1 "$COMMIT" --pretty=format:%s | sed s/'Merge .*#\([0-9]*\):.*'/'\1'/)
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TITLE="$TITLE $PRNUM,"
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BODY=$(printf "%s\n * %s" "$BODY" "$(git log -1 "$COMMIT" --pretty=format:%s | sed s/'Merge '//)")
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done
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# Remove trailing ","
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TITLE=${TITLE%?}
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BODY+=$(cat <<'EOF'
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Usage hints:
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* If this PR has merge conflicts, resolve these by switching to the PR branch and merging the base branch into it using `git merge <base-branch>`.
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* To show the conflict resolution diff from an existing merge commit, use `git show --remerge-diff <merge-commit>`.
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* In case you are recreating the PR branch locally, you can (during the conflict resolution state) replay this conflict resolution diff using `git read-tree --reset -u <merge-commit>`.
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Be aware that this may discard your index as well as the uncommitted changes and untracked files in your worktree.
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EOF
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)
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### Create a sync branch locally.
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SYNC_BRANCH="sync-$(git rev-parse --short "$UPSTREAM_REF")"
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# This will error out if the branch already exists, which is what we want.
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git branch --no-track "$SYNC_BRANCH" "$UPSTREAM_REF"
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### Print the PR metadata
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echo "-----------------------------------"
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echo "$TITLE"
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echo "-----------------------------------"
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echo "$BODY"
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echo "-----------------------------------"
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### Generate the helper script for creating the PR
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FNAME="gh-pr-create.sh"
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# Escape single quote ' -> '\''
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quote() {
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local quoted=${1//\'/\'\\\'\'}
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printf "%s" "$quoted"
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}
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TITLE=$(quote "$TITLE")
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BODY=$(quote "$BODY")
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cat <<EOT > "$FNAME"
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#!/bin/sh
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TITLE='$TITLE'
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BODY='$BODY'
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SYNC_BRANCH='$SYNC_BRANCH'
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BASE_BRANCH='$BASE_BRANCH'
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gh pr create --base "\$BASE_BRANCH" --head "\$SYNC_BRANCH" --title "\$TITLE" --body "\$BODY" "\$@"
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EOT
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chmod +x "$FNAME"
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echo "Successfully created local sync branch $SYNC_BRANCH starting at $UPSTREAM_REF."
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echo
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echo "You can now:"
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echo " 1. Optionally resolve merge conflicts by merging $BASE_BRANCH into $SYNC_BRANCH."
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echo " 2. Push $SYNC_BRANCH to some GitHub remote."
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echo " 3. Run ./$FNAME to create a pull request. (Tip: Pass --dry-run first.)"
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if [ "${SWITCH:-false}" = true ]; then
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echo
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echo "Trying to switch to the sync branch..."
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echo
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git switch "$SYNC_BRANCH"
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fi
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