Release: refactor the way we keep track of release notes

Now the release branch does not contains the release commit anymore.
Instead, we regenerate the full release notes each time we have to
(release candidate creation and final release).

Two side effects:
  - The date is now showing the date of the operation and no longer
    the date of the release candidate (so release will be correctly dated)
  - The release notes show the release candidate number :)

Tested: bazel test //scripts/release/... + build README.md

--
Change-Id: Ia249bbdc0d6ed240bd969f24aa013f709f9a0a74
Reviewed-on: https://cr.bazel.build/7338
PiperOrigin-RevId: 140841432
MOS_MIGRATED_REVID=140841432

scripts/release/common.sh

diff --git a/scripts/release/common.sh b/scripts/release/common.sh
index e17cedc..2f0bc0d 100755
--- a/scripts/release/common.sh
+++ b/scripts/release/common.sh
@@ -49,6 +49,35 @@
   git notes --ref=release show "$@" 2>/dev/null | xargs echo || true
 }
 
+# Get the short hash of a commit
+function git_commit_shorthash() {
+  git rev-parse --short "${1}"
+}
+
+# Get the subject (first line of the commit message) of a commit
+function git_commit_subject() {
+  git show -s --pretty=format:%s "$@"
+}
+
+# Get the list of commit hashes between two revisions
+function git_log_hash() {
+  local baseline="$1"
+  local head="$2"
+  shift 2
+  git log --pretty=format:%H "${baseline}".."${head}" "$@"
+}
+
+# Extract the full release name from the git notes
+function get_full_release_name() {
+  local name="$(get_release_name "$@")"
+  local rc="$(get_release_candidate "$@")"
+  if [ -n "${rc}" ]; then
+    echo "${name}rc${rc}"
+  else
+    echo "${name}"
+  fi
+}
+
 # Extract the release notes from the git notes
 function get_release_notes() {
   git notes --ref=release-notes show "$@" 2>/dev/null || true
@@ -66,3 +95,98 @@
   fi
   echo "${branch_name}"
 }
+
+# fmt behaves differently on *BSD and on GNU/Linux, use fold.
+function wrap_text() {
+  fold -s -w $1 | sed 's/ *$//'
+}
+
+# Create the revision information given a list of commits. The first
+# commit should be the baseline, and the other ones are the cherry-picks.
+# The result is of the form:
+# Baseline: BASELINE_COMMIT
+#
+# Cherry picks:
+#    + CHERRY_PICK1: commit message summary of the CHERRY_PICK1. This
+#                    message will be wrapped into 70 columns.
+#    + CHERRY_PICK2: commit message summary of the CHERRY_PICK2.
+function create_revision_information() {
+  echo "Baseline: $(git_commit_shorthash "${1}")"
+  local first=1
+  shift
+  while [ -n "${1-}" ]; do
+    if [[ "$first" -eq 1 ]]; then
+      echo -e "\nCherry picks:"
+      first=0
+    fi
+    local hash="$(git_commit_shorthash "${1}")"
+    local subject="$(git_commit_subject $hash)"
+    local lines=$(echo "$subject" | wrap_text 56)  # 14 leading spaces.
+    echo "   + $hash: $lines" | head -1
+    echo "$lines" | tail -n +2 | sed 's/^/              /'
+    shift
+  done
+}
+
+# Get the baseline of master.
+# Args: $1: release branch, default to HEAD
+function get_release_baseline() {
+  git merge-base master "${1:-HEAD}"
+}
+
+# Get the list of cherry-picks since master
+# Args:
+#   $1: branch, default to HEAD
+#   $2: baseline change, default to $(get_release_baseline $1)
+function get_cherrypicks() {
+  local branch="${1:-HEAD}"
+  local baseline="${2:-$(get_release_baseline "${branch}")}"
+  # List of changes since the baseline on the release branch
+  local changes="$(git_log_hash "${baseline}" "${branch}" --reverse)"
+  # List of changes since the baseline on the master branch, and their patch-id
+  local master_changes="$(git_log_hash "${baseline}" master | xargs git show | git patch-id)"
+  # Now for each changes on the release branch
+  for i in ${changes}; do
+    # Find the change with the same patch-id on the master branch
+    echo "${master_changes}" \
+      | grep "^$(git show "$i" | git patch-id | cut -d " " -f 1)" \
+      | cut -d " " -f 2
+  done
+}
+
+# Generate the title of the release with the date from the release name ($1).
+function get_release_title() {
+  echo "Release ${1} ($(date +%Y-%m-%d))"
+}
+
+# Generate the release message to be added to the changelog
+# from the release notes for release $1
+function generate_release_message() {
+  local release_name="$1"
+  local branch="${2:-HEAD}"
+  local baseline="$(get_release_baseline "${branch}")"
+  local cherrypicks="$(get_cherrypicks "${branch}" "${baseline}")"
+
+cat <<EOF
+$(get_release_title "$release_name")
+
+$(create_revision_information $baseline $cherrypicks)
+
+$(get_release_notes "${branch}")
+EOF
+}
+
+# Returns the release notes for the CHANGELOG.md taken from either from
+# the notes for a release candidate or from the commit message for a
+# full release.
+function get_full_release_notes() {
+  local release_name="$(get_full_release_name "$@")"
+
+  if [[ "${release_name}" =~ rc[0-9]+$ ]]; then
+    # Release candidate, we need to generate from the notes
+    generate_release_message "${release_name}" "$@"
+  else
+    # Full release, returns the commit message
+    git_commit_msg "$@"
+  fi
+}