releng: fix the git push

This was broken because gerrit requires that the revision actually
is known before it is pushed as a tag.

Also, arguably this fixes the original problem mentioned in
https://git.lix.systems/lix-project/lix/issues/439

Change-Id: I0373ac01584440f18d32b8da5699bb359cc2c89a

releng/create_release.xsh

@@ -2,6 +2,7 @@ import json
 import subprocess
 import itertools
 import textwrap
+import logging
 from pathlib import Path
 import tempfile
 import hashlib
@@ -15,6 +16,8 @@ from .version import VERSION, RELEASE_NAME, MAJOR, OFFICIAL_RELEASE
 from .gitutils import verify_are_on_tag, git_preconditions
 from . import release_notes
 
+log = logging.getLogger(__name__)
+
 $RAISE_SUBPROC_ERROR = True
 $XONSH_SHOW_TRACEBACK = True
 
@@ -55,6 +58,9 @@ def official_release_commit_tag(force_tag=False):
     git commit -m @(message)
     git tag @(['-f'] if force_tag else []) -a -m @(message) @(VERSION)
 
+    with open('releng/prev-git-branch.txt', 'w') as fh:
+        fh.write(prev_branch)
+
     return prev_branch
 
 
@@ -235,8 +241,24 @@ def upload_artifacts(env: RelengEnvironment, noconfirm=False, no_check_git=False
     print('[+] Upload manual')
     upload_manual(env)
 
-    print('[+] git push tag')
-    git push @(['-f'] if force_push_tag else []) @(env.git_repo) f'{VERSION}:refs/tags/{VERSION}'
+    prev_branch = None
+    try:
+        with open('releng/prev-git-branch.txt', 'r') as fh:
+            prev_branch = fh.read().strip()
+    except FileNotFoundError:
+        log.warn('Cannot find previous git branch file, skipping pushing git objects')
+
+    if prev_branch:
+        print('[+] git push to the repo')
+        # We have to push the ref to gerrit for review at least such that the
+        # commit is known, before we can push it as a tag.
+        if env.git_repo_is_gerrit:
+            git push @(env.git_repo) f'{prev_branch}:refs/for/{prev_branch}'
+        else:
+            git push @(env.git_repo) f'{prev_branch}:{prev_branch}'
+
+        print('[+] git push tag')
+        git push @(['-f'] if force_push_tag else []) @(env.git_repo) f'{VERSION}:refs/tags/{VERSION}'
 
 
 def do_tag_merge(force_tag=False, no_check_git=False):

releng/environment.py

@@ -52,6 +52,7 @@ class RelengEnvironment:
     releases_bucket: str
     docs_bucket: str
     git_repo: str
+    git_repo_is_gerrit: bool
 
     docker_targets: list[DockerTarget]
 
@@ -79,6 +80,7 @@ STAGING = RelengEnvironment(
     cache_store_overlay={'secret-key': 'staging.key'},
     releases_bucket='s3://staging-releases',
     git_repo='ssh://git@git.lix.systems/lix-project/lix-releng-staging',
+    git_repo_is_gerrit=False,
     docker_targets=[
         # latest will be auto tagged if appropriate
         DockerTarget('git.lix.systems/lix-project/lix-releng-staging',
@@ -113,6 +115,7 @@ PROD = RelengEnvironment(
     cache_store_overlay={'secret-key': 'prod.key'},
     releases_bucket='s3://releases',
     git_repo=guess_gerrit_remote(),
+    git_repo_is_gerrit=True,
     docker_targets=[
         # latest will be auto tagged if appropriate
         DockerTarget('git.lix.systems/lix-project/lix',