ci/request-reviews/verify-base-branch.sh

   1 #!/usr/bin/env bash
   2
   3 # Check that a PR doesn't include commits from other development branches.
   4 # Fails with next steps if it does
   5
   6 set -euo pipefail
   7 tmp=$(mktemp -d)
   8 trap 'rm -rf "$tmp"' exit
   9 SCRIPT_DIR=$(dirname "$0")
  10
  11 log() {
  12     echo "$@" >&2
  13 }
  14
  15 # Small helper to check whether an element is in a list
  16 # Usage: `elementIn foo "${list[@]}"`
  17 elementIn() {
  18     local e match=$1
  19     shift
  20     for e; do
  21         if [[ "$e" == "$match" ]]; then
  22             return 0
  23         fi
  24     done
  25     return 1
  26 }
  27
  28 if (( $# < 6 )); then
  29     log "Usage: $0 LOCAL_REPO HEAD_REF BASE_REPO BASE_BRANCH PR_REPO PR_BRANCH"
  30     exit 1
  31 fi
  32 localRepo=$1
  33 headRef=$2
  34 baseRepo=$3
  35 baseBranch=$4
  36 prRepo=$5
  37 prBranch=$6
  38
  39 # All development branches
  40 devBranchPatterns=()
  41 while read -r pattern; do
  42     if [[ "$pattern" != '#'* ]]; then
  43         devBranchPatterns+=("$pattern")
  44     fi
  45 done < "$SCRIPT_DIR/dev-branches.txt"
  46
  47 git -C "$localRepo" branch --list --format "%(refname:short)" "${devBranchPatterns[@]}" > "$tmp/dev-branches"
  48 readarray -t devBranches < "$tmp/dev-branches"
  49
  50 if [[ "$baseRepo" == "$prRepo" ]] && elementIn "$prBranch" "${devBranches[@]}"; then
  51     log "This PR merges $prBranch into $baseBranch, no commit check necessary"
  52     exit 0
  53 fi
  54
  55 # The current merge base of the PR
  56 prMergeBase=$(git -C "$localRepo" merge-base "$baseBranch" "$headRef")
  57 log "The PR's merge base with the base branch $baseBranch is $prMergeBase"
  58
  59 # This is purely for debugging
  60 git -C "$localRepo" rev-list --reverse "$baseBranch".."$headRef" > "$tmp/pr-commits"
  61 log "The PR includes these $(wc -l < "$tmp/pr-commits") commits:"
  62 cat <"$tmp/pr-commits" >&2
  63
  64 for testBranch in "${devBranches[@]}"; do
  65
  66     if [[ -z "$(git -C "$localRepo" rev-list -1 --since="1 month ago" "$testBranch")" ]]; then
  67         log "Not checking $testBranch, was inactive for the last month"
  68         continue
  69     fi
  70     log "Checking if commits from $testBranch are included in the PR"
  71
  72     # We need to check for any commits that are in the PR which are also in the test branch.
  73     # We could check each commit from the PR individually, but that's unnecessarily slow.
  74     #
  75     # This does _almost_ what we want: `git rev-list --count headRef testBranch ^baseBranch`,
  76     # except that it includes commits that are reachable from _either_ headRef or testBranch,
  77     # instead of restricting it to ones reachable by both
  78
  79     # Easily fixable though, because we can use `git merge-base testBranch headRef`
  80     # to get the least common ancestor (aka merge base) commit reachable by both.
  81     # If the branch being tested is indeed the right base branch,
  82     # this is then also the commit from that branch that the PR is based on top of.
  83     testMergeBase=$(git -C "$localRepo" merge-base "$testBranch" "$headRef")
  84
  85     # And then use the `git rev-list --count`, but replacing the non-working
  86     # `headRef testBranch` with the merge base of the two.
  87     extraCommits=$(git -C "$localRepo" rev-list --count "$testMergeBase" ^"$baseBranch")
  88
  89     if (( extraCommits != 0 )); then
  90         log -e "\e[33m"
  91         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:"
  92         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"
  93         echo "- If the changes should go to the $baseBranch branch, rebase your PR onto the merge base with the $baseBranch branch:"
  94         echo "  \`\`\`bash"
  95         echo "  # git rebase --onto \$(git merge-base upstream/$baseBranch HEAD) \$(git merge-base upstream/$testBranch HEAD)"
  96         echo "  git rebase --onto $prMergeBase $testMergeBase"
  97         echo "  git push --force-with-lease"
  98         echo "  \`\`\`"
  99         log -e "\e[m"
 100         exit 1
 101     fi
 102 done
 103
 104 log "Base branch is correct, no commits from development branches are included"