ci: add a workflow to check for entrypoint tags

Check check-entrypoint.sh comment for explanation of what entrypoint tag
is. The workflow fails if current branch does not have a most recent
entrypoint tag that it should have.

NO_TEST=ci
NO_CHANGELOG=ci
NO_DOC=ci

.github/workflows/tree.yml

@@ -0,0 +1,45 @@
+name: tree
+
+on:
+  push:
+    branches:
+      - 'master'
+      - 'release/**'
+
+concurrency:
+  # Update of a developer branch cancels the previously scheduled workflow
+  # run for this branch. However, the 'master' branch, release branch, and
+  # tag workflow runs are never canceled.
+  #
+  # We use a trick here: define the concurrency group as 'workflow run ID' +
+  # 'workflow run attempt' because it is a unique combination for any run.
+  # So it effectively discards grouping.
+  #
+  # Important: we cannot use `github.sha` as a unique identifier because
+  # pushing a tag may cancel a run that works on a branch push event.
+  group: ${{ (
+    github.ref == 'refs/heads/master' ||
+    startsWith(github.ref, 'refs/heads/release/') ||
+    startsWith(github.ref, 'refs/tags/')) &&
+    format('{0}-{1}', github.run_id, github.run_attempt) ||
+    format('{0}-{1}', github.workflow, github.ref) }}
+  cancel-in-progress: true
+
+jobs:
+  entrypoint-tag:
+    if: github.repository == 'tarantool/tarantool'
+    runs-on: ubuntu-20.04-self-hosted
+
+    steps:
+      - name: Prepare checkout
+        uses: tarantool/actions/prepare-checkout@master
+      - name: Sources checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - run: ./tools/check-entrypoint.sh
+      - name: Send VK Teams message on failure
+        if: failure()
+        uses: ./.github/actions/report-job-status
+        with:
+          bot-token: ${{ secrets.VKTEAMS_BOT_TOKEN }}

tools/check-entrypoint.sh

@@ -0,0 +1,87 @@
+#!/bin/bash
+# vim: set ts=4 sts=4 sw=4 et:
+#
+# This script checks that current branch has most recent entrypoint tag.
+# There are 2 cases when we require entrypoint tag.
+#
+# 1. After release tag (like 2.10.5, 2.11.0 etc). We require that the next
+# commit has annotated tag
+#
+# 2. After branching. For example we develop 3.0.0 in master. And decide
+# to release 3.0.0. We fork release/3.0 branch. The first commit after
+# fork in release/3.0 branch is required to has annotated tag (like 3.0.0-rc1
+# or something). The first commit after fork in master branch is required
+# to has annotated entrypoint tag too.
+#
+# Note that in both cases we do not check that required annotated tag has
+# "entrypoint" or "rc" in the name.
+#
+# We check for most recent entrypoint tag only. Most recent in a sense that
+# for example if there are tags for releases 2.10.0 and 2.10.1 on current
+# branch the script only check for entrypoint tag after 2.10.1 tag.
+
+set -eo pipefail
+
+error() {
+   echo "$@" 1>&2
+   exit 1
+}
+
+if ! git --version >/dev/null 2>&1; then
+    error "git must be installed."
+fi
+
+#########
+# Case 1.
+#########
+
+# Match digit only release tags like 2.10.0.
+pattern='^[[:digit:]]+\.[[:digit:]]+\.[[:digit:]]+$'
+# Show most recent tag in the HEAD ancestry
+tag=`git describe --abbrev=0`
+# If it is a release tag.
+if [[ "$tag" =~ $pattern ]]; then
+    # Find the commit just after the release tag in the HEAD ancestry.
+    # It is not tagged as entrypoint because it was not seen by the
+    # describe command above.
+    entrypoint=`git rev-list HEAD ^$tag | tail -n1`
+    if [[ $entrypoint ]]; then
+        error "Missing entrypoint tag for commit $entrypoint after release"\
+              "tag $tag."
+    fi
+fi
+
+#########
+# Case 2.
+#########
+
+# Find current branch (report HEAD for 'detached HEAD' state).
+branch=`git rev-parse --abbrev-ref HEAD`
+if [[ "$branch" =~ ^(master|release/.*)$ ]]; then
+    # We need to find the commit that starts this branch (i.e. that the first
+    # commit on this branch after the commit that is common for two branches.)
+    #
+    # In order to archive this we find all the commits of this branch that
+    # are not on other branches from release/* && master set.
+    #
+    # Unfortunately I did not find a way to set arguments for git rev-list
+    # without this branch.
+    if [[ "$branch" = master ]]; then
+        not_remotes="--remotes=origin/release/*"
+    else
+        not_remotes="--exclude origin/$branch --remotes=origin/release/* origin/master"
+    fi
+    entrypoint=`git rev-list HEAD --not $not_remotes | tail -n1`
+    if [[ $entrypoint ]]; then
+        # Show most recent tag in the HEAD ancestry
+        tag=`git describe --abbrev=0`
+        tag_commit=`git rev-list -n 1 $tag`
+        if [[ $tag_commit != $entrypoint ]]; then
+            error "Missing tag for commit $entrypoint after branching."\
+                  "It should be an entrypoint tag or a tag for a downstream"\
+                  "branch."
+        fi
+    fi
+fi
+
+echo OK