[ADD] *: PR backport wizard

This is not a full user-driven backport thingie for now, just one
admins can use to facilitate thing and debug issues with the
system. May eventually graduate to a frontend feature.

Fixes #925

forwardport/models/forwardport.py

@@ -202,7 +202,7 @@ def _complete_batches(self):
             # NOTE: ports the new source everywhere instead of porting each
             #       PR to the next step as it does not *stop* on conflict
             repo = git.get_local(source.repository)
-            conflict, head = source._create_fp_branch(repo, target)
+            conflict, head = source._create_port_branch(repo, target, forward=True)
             repo.push(git.fw_url(pr.repository), f'{head}:refs/heads/{ref}')
 
             remote_target = repository.fp_remote_target
@@ -302,7 +302,7 @@ def _process_item(self):
                     return
 
                 repo = git.get_local(previous.repository)
-                conflicts, new_head = previous._create_fp_branch(repo, child.target)
+                conflicts, new_head = previous._create_port_branch(repo, child.target, forward=True)
 
                 if conflicts:
                     _, out, err, _ = conflicts

forwardport/models/project.py

@@ -34,6 +34,8 @@
 from odoo.addons.runbot_merge.models.pull_requests import Branch
 from odoo.addons.runbot_merge.models.stagings_create import Message
 
+Conflict = tuple[str, str, str, list[str]]
+
 DEFAULT_DELTA = dateutil.relativedelta.relativedelta(days=3)
 
 _logger = logging.getLogger('odoo.addons.forwardport')
@@ -287,17 +289,29 @@ def commits(self):
         return sorted(commits, key=lambda c: idx[c['sha']])
 
 
-    def _create_fp_branch(self, source, target_branch):
+    def _create_port_branch(
+            self,
+            source: git.Repo,
+            target_branch: Branch,
+            *,
+            forward: bool,
+    ) -> tuple[typing.Optional[Conflict], str]:
         """ Creates a forward-port for the current PR to ``target_branch`` under
         ``fp_branch_name``.
 
-        :param target_branch: the branch to port forward to
-        :rtype: (None | (str, str, str, list[commit]), Repo)
+        :param source: the git repository to work with / in
+        :param target_branch: the branch to port ``self`` to
+        :param forward: whether this is a forward (``True``) or a back
+                        (``False``) port
+        :returns: a conflict if one happened, and the head of the port branch
+                  (either a succcessful port of the entire `self`, or a conflict
+                  commit)
         """
         logger = _logger.getChild(str(self.id))
         root = self.root_id
         logger.info(
-            "Forward-porting %s (%s) to %s",
+            "%s %s (%s) to %s",
+            "Forward-porting" if forward else "Back-porting",
             self.display_name, root.display_name, target_branch.name
         )
         fetch = source.with_config(stdout=subprocess.PIPE, stderr=subprocess.STDOUT).fetch()

forwardport/tests/test_backport.py

@@ -0,0 +1,117 @@
+from xmlrpc.client import Fault
+
+import pytest
+
+from utils import make_basic, Commit, to_pr, seen
+
+
+@pytest.fixture
+def repo(env, config, make_repo):
+    repo, _ = make_basic(env, config, make_repo, statuses="default")
+    return repo
+
+@pytest.fixture
+def pr_id(env, repo, config):
+    with repo:
+        repo.make_commits('c', Commit("c", tree={'x': '1'}), ref='heads/aref')
+        pr = repo.make_pr(target='c', head='aref')
+        repo.post_status('aref', 'success')
+        pr.post_comment('hansen r+', config['role_reviewer']['token'])
+    env.run_crons()
+    with repo:
+        repo.post_status('staging.c', 'success')
+    env.run_crons()
+    pr_id = to_pr(env, pr)
+    assert pr_id.merge_date
+    return pr_id
+
+@pytest.fixture
+def backport_id(env, pr_id):
+    action = pr_id.backport()
+    backport_id = env[action['res_model']].browse([action['res_id']])
+    assert backport_id._name == 'runbot_merge.pull_requests.backport'
+    assert backport_id
+    return backport_id
+
+def test_golden_path(env, repo, config, pr_id, backport_id, users):
+    branch_a, branch_b, _branch_c = env['runbot_merge.branch'].search([], order='name')
+    backport_id.target = branch_a.id
+    act2 = backport_id.action_apply()
+    env.run_crons()  # run cron to update labels
+
+    _, bp_id = env['runbot_merge.pull_requests'].search([], order='number')
+    assert bp_id.limit_id == branch_b
+    assert bp_id._name == act2['res_model']
+    assert bp_id.id == act2['res_id']
+    bp_head = repo.commit(bp_id.head)
+    assert repo.read_tree(bp_head) == {
+        'f': 'e',
+        'x': '1',
+    }
+    assert bp_head.message == f"""c
+
+X-original-commit: {pr_id.head}\
+"""
+    assert bp_id.message == f"[Backport] c\n\nBackport of {pr_id.display_name}"
+    assert repo.get_pr(bp_id.number).labels == {"backport"}
+
+    # check that the backport can actually be merged and forward-ports successfully...
+    with repo:
+        repo.post_status(bp_id.head, 'success')
+        repo.get_pr(bp_id.number).post_comment("hansen r+", config['role_reviewer']['token'])
+    env.run_crons()
+    with repo:
+        repo.post_status('staging.a', 'success')
+    env.run_crons()
+    _pr, _backport, fw_id = env['runbot_merge.pull_requests'].search([], order='number')
+    fw_pr = repo.get_pr(fw_id.number)
+    assert fw_pr.comments == [
+        seen(env, fw_pr, users),
+        (users['user'], '''\
+@{user} @{reviewer} this PR targets b and is the last of the forward-port chain.
+
+To merge the full chain, use
+> @hansen r+
+
+More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port
+'''.format_map(users)),
+    ]
+
+def test_conflict(env, repo, config, backport_id):
+    with repo:
+        repo.make_commits('a', Commit('conflict', tree={'x': '-1'}), ref='heads/a', make=False)
+
+    branch_a, _branch_b, _branch_c = env['runbot_merge.branch'].search([], order='name')
+    backport_id.target = branch_a.id
+    with pytest.raises(Fault) as exc:
+        backport_id.action_apply()
+    assert exc.value.faultString == """\
+backport conflict:
+
+Auto-merging x
+CONFLICT (add/add): Merge conflict in x
+"""
+
+def test_target_error(env, config, backport_id):
+    branch_a, _branch_b, branch_c = env['runbot_merge.branch'].search([], order='name')
+    with pytest.raises(Fault) as exc:
+        backport_id.action_apply()
+    assert exc.value.faultString == "A backport needs a backport target"
+
+    backport_id.target = branch_c.id
+    with pytest.raises(Fault) as exc:
+        backport_id.action_apply()
+    assert exc.value.faultString == "The backport branch needs to be before the source's branch (got 'c' and 'c')"
+
+    backport_id.target = branch_a.id
+    backport_id.action_apply()
+
+@pytest.mark.skip(
+    reason="Currently no way to make just the PR creation fail, swapping the "
+           "fp_github_token for an invalid one breaks git itself"
+)
+def test_pr_fail(env, config, repo, pr_id, backport_id):
+    backport_id.target = env['runbot_merge.branch'].search([], order='name', limit=1).id
+    with pytest.raises(Fault) as exc:
+        backport_id.action_apply()
+    assert exc.value.faultString == 'Backport PR creation failure: '

runbot_merge/models/__init__.py

@@ -8,5 +8,6 @@
 from . import project_freeze
 from . import stagings_create
 from . import staging_cancel
+from . import backport
 from . import events_sources
 from . import crons

runbot_merge/models/backport/__init__.py

@@ -0,0 +1,140 @@
+import logging
+import re
+import secrets
+import subprocess
+
+import requests
+
+from odoo import models, fields
+from odoo.exceptions import UserError
+
+from ..batch import Batch
+from ..project import Project
+from ..pull_requests import Repository
+from ... import git
+
+_logger = logging.getLogger(__name__)
+
+
+class PullRequest(models.Model):
+    _inherit = 'runbot_merge.pull_requests'
+
+    id: int
+    display_name: str
+    project: Project
+    repository: Repository
+    batch_id: Batch
+
+    def backport(self) -> dict:
+        if len(self) != 1:
+            raise UserError(f"Backporting works one PR at a time, got {len(self)}")
+
+        if len(self.batch_id.prs) > 1:
+            raise UserError("Automatic backport of multi-pr batches is not currently supported")
+
+        if not self.project.fp_github_token:
+            raise UserError(f"Can not backport {self.display_name}: no token on project {self.project.display_name}")
+
+        if not self.repository.fp_remote_target:
+            raise UserError(f"Can not backport {self.display_name}: no remote on {self.project.display_name}")
+
+        w = self.env['runbot_merge.pull_requests.backport'].create({
+            'pr_id': self.id,
+        })
+        return {
+            'type': 'ir.actions.act_window',
+            'name': f"Backport of {self.display_name}",
+            'views': [('form', False)],
+            'target': 'new',
+            'res_model': w._name,
+            'res_id': w.id,
+        }
+
+class PullRequestBackport(models.TransientModel):
+    _name = 'runbot_merge.pull_requests.backport'
+    _rec_name = 'pr_id'
+
+    pr_id = fields.Many2one('runbot_merge.pull_requests', required=True)
+    target = fields.Many2one('runbot_merge.branch')
+
+    def action_apply(self) -> dict:
+        if not self.target:
+            raise UserError("A backport needs a backport target")
+
+        project = self.pr_id.project
+        branches = project._forward_port_ordered().ids
+        source = self.pr_id.source_id or self.pr_id
+        source_idx = branches.index(source.target.id)
+        if branches.index(self.target.id) >= source_idx:
+            raise UserError(
+                "The backport branch needs to be before the source's branch "
+                f"(got {self.target.name!r} and {source.target.name!r})"
+            )
+
+        _logger.info(
+            "backporting %s (on %s) to %s",
+            self.pr_id.display_name,
+            self.pr_id.target.name,
+            self.target.name,
+        )
+
+        bp_branch = "%s-%s-%s-bp" % (
+            self.target.name,
+            self.pr_id.refname,
+            secrets.token_urlsafe(3),
+        )
+        repo_id = self.pr_id.repository
+        repo = git.get_local(repo_id)
+
+        old_map = self.pr_id.commits_map
+        self.pr_id.commits_map = "{}"
+        conflict, head = self.pr_id._create_port_branch(repo, self.target, forward=False)
+        self.pr_id.commits_map = old_map
+
+        if conflict:
+            feedback = "\n".join(filter(None, conflict[1:3]))
+            raise UserError(f"backport conflict:\n\n{feedback}")
+        repo.push(git.fw_url(repo_id), f"{head}:refs/heads/{bp_branch}")
+
+        self.env.cr.execute('LOCK runbot_merge_pull_requests IN SHARE MODE')
+
+        owner, _repo = repo_id.fp_remote_target.split('/', 1)
+        message = source.message + f"\n\nBackport of {self.pr_id.display_name}"
+        title, body = re.fullmatch(r'(?P<title>[^\n]+)\n*(?P<body>.*)', message, flags=re.DOTALL).groups()
+
+        r = requests.post(
+            f'https://api.github.com/repos/{repo_id.name}/pulls',
+            headers={'Authorization': f'token {project.fp_github_token}'},
+            json={
+                'base': self.target.name,
+                'head': f'{owner}:{bp_branch}',
+                'title': '[Backport]' + ('' if title[0] == '[' else ' ') + title,
+                'body': body
+            }
+        )
+        if not r.ok:
+            raise UserError(f"Backport PR creation failure: {r.text}")
+
+        backport = self.env['runbot_merge.pull_requests']._from_gh(r.json())
+        _logger.info("Created backport %s for %s", backport.display_name, self.pr_id.display_name)
+
+        backport.write({
+            'merge_method': self.pr_id.merge_method,
+            # the backport's own forwardport should stop right before the
+            # original PR by default
+            'limit_id': branches[source_idx - 1],
+        })
+        self.env['runbot_merge.pull_requests.tagging'].create({
+            'repository': repo_id.id,
+            'pull_request': backport.number,
+            'tags_add': ['backport'],
+        })
+        # scheduling fp followup probably doesn't make sense since we don't copy the fw_policy...
+
+        return {
+            'type': 'ir.actions.act_window',
+            'name': "new backport",
+            'views': [('form', False)],
+            'res_model': backport._name,
+            'res_id': backport.id,
+        }

runbot_merge/models/batch.py

@@ -326,7 +326,7 @@ def _port_forward(self):
         conflicts = {}
         for pr in prs:
             repo = git.get_local(pr.repository)
-            conflicts[pr], head = pr._create_fp_branch(repo, target)
+            conflicts[pr], head = pr._create_port_branch(repo, target, forward=True)
 
             repo.push(git.fw_url(pr.repository), f"{head}:refs/heads/{new_branch}")
 

runbot_merge/security/ir.model.access.csv

@@ -32,3 +32,4 @@ access_runbot_merge_review_rights_2,Users can see partners,model_res_partner_rev
 access_runbot_merge_review_override_2,Users can see partners,model_res_partner_override,base.group_user,1,0,0,0
 access_runbot_merge_pull_requests_feedback_template,access_runbot_merge_pull_requests_feedback_template,runbot_merge.model_runbot_merge_pull_requests_feedback_template,base.group_system,1,1,0,0
 access_runbot_merge_patch,Patcher access,runbot_merge.model_runbot_merge_patch,runbot_merge.group_patcher,1,1,1,0
+access_runbot_merge_backport_admin,Admin access to backport wizard,model_runbot_merge_pull_requests_backport,runbot_merge.group_admin,1,1,1,0