depot/third_party/nixpkgs/ci/request-reviews/verify-base-branch.sh

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#!/usr/bin/env bash
# Check that a PR doesn't include commits from other development branches.
# Fails with next steps if it does
set -euo pipefail
tmp=$(mktemp -d)
trap 'rm -rf "$tmp"' exit
SCRIPT_DIR=$(dirname "$0")
log() {
echo "$@" >&2
}
# Small helper to check whether an element is in a list
# Usage: `elementIn foo "${list[@]}"`
elementIn() {
local e match=$1
shift
for e; do
if [[ "$e" == "$match" ]]; then
return 0
fi
done
return 1
}
if (( $# < 6 )); then
log "Usage: $0 LOCAL_REPO HEAD_REF BASE_REPO BASE_BRANCH PR_REPO PR_BRANCH"
exit 1
fi
localRepo=$1
headRef=$2
baseRepo=$3
baseBranch=$4
prRepo=$5
prBranch=$6
# All development branches
devBranchPatterns=()
while read -r pattern; do
if [[ "$pattern" != '#'* ]]; then
devBranchPatterns+=("$pattern")
fi
done < "$SCRIPT_DIR/dev-branches.txt"
git -C "$localRepo" branch --list --format "%(refname:short)" "${devBranchPatterns[@]}" > "$tmp/dev-branches"
readarray -t devBranches < "$tmp/dev-branches"
if [[ "$baseRepo" == "$prRepo" ]] && elementIn "$prBranch" "${devBranches[@]}"; then
log "This PR merges $prBranch into $baseBranch, no commit check necessary"
exit 0
fi
# The current merge base of the PR
prMergeBase=$(git -C "$localRepo" merge-base "$baseBranch" "$headRef")
log "The PR's merge base with the base branch $baseBranch is $prMergeBase"
# This is purely for debugging
git -C "$localRepo" rev-list --reverse "$baseBranch".."$headRef" > "$tmp/pr-commits"
log "The PR includes these $(wc -l < "$tmp/pr-commits") commits:"
cat <"$tmp/pr-commits" >&2
for testBranch in "${devBranches[@]}"; do
if [[ -z "$(git -C "$localRepo" rev-list -1 --since="1 month ago" "$testBranch")" ]]; then
log "Not checking $testBranch, was inactive for the last month"
continue
fi
log "Checking if commits from $testBranch are included in the PR"
# We need to check for any commits that are in the PR which are also in the test branch.
# We could check each commit from the PR individually, but that's unnecessarily slow.
#
# This does _almost_ what we want: `git rev-list --count headRef testBranch ^baseBranch`,
# except that it includes commits that are reachable from _either_ headRef or testBranch,
# instead of restricting it to ones reachable by both
# Easily fixable though, because we can use `git merge-base testBranch headRef`
# to get the least common ancestor (aka merge base) commit reachable by both.
# If the branch being tested is indeed the right base branch,
# this is then also the commit from that branch that the PR is based on top of.
testMergeBase=$(git -C "$localRepo" merge-base "$testBranch" "$headRef")
# And then use the `git rev-list --count`, but replacing the non-working
# `headRef testBranch` with the merge base of the two.
extraCommits=$(git -C "$localRepo" rev-list --count "$testMergeBase" ^"$baseBranch")
if (( extraCommits != 0 )); then
log -e "\e[33m"
echo "The PR's base branch is set to $baseBranch, but $extraCommits commits from the $testBranch branch are included. Make sure you know the [right base branch for your changes](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#branch-conventions), then:"
echo "- If the changes should go to the $testBranch branch, [change the base branch](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-base-branch-of-a-pull-request) to $testBranch"
echo "- If the changes should go to the $baseBranch branch, rebase your PR onto the merge base with the $baseBranch branch:"
echo " \`\`\`bash"
echo " # git rebase --onto \$(git merge-base upstream/$baseBranch HEAD) \$(git merge-base upstream/$testBranch HEAD)"
echo " git rebase --onto $prMergeBase $testMergeBase"
echo " git push --force-with-lease"
echo " \`\`\`"
log -e "\e[m"
exit 1
fi
done
log "Base branch is correct, no commits from development branches are included"