Merge ~racb/git-ubuntu:clone-remote-tracking into git-ubuntu:main

[Robie Basak]

Make Jenkins happy

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:e0c2907afa264504df8a25b9470da06a7b38c5cc
https://jenkins.canonical.com/server-team/job/git-ubuntu-ci/39/
Executed test runs:
    SUCCESS: VM Setup
    SUCCESS: Build
    SUCCESS: VM Reset
    SUCCESS: Unit Tests
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
https://jenkins.canonical.com/server-team/job/git-ubuntu-ci/39//rebuild

review: Approve (continuous-integration)

[Athos Ribeiro (athos-ribeiro)]

Thanks, Robie.

A helper or a new function could be extracted from the 2 new test cases (test_create_tracking_branch*) since most of the code in those are duplicated. This shouldn't be a blocker here though since they are short test cases (however, if we ever need to use the same snippets for another test, we should consider extracting that duplicated code snippet somehow).

LGTM

review: Approve

[Robie Basak (racb)]

Thank you Athos for the review! I agree on the duplication - it's not worth the trade-off for two, but if we need the pattern more, then I would factor the duplication out into a test fixture.

diff --git a/gitubuntu/clone.py b/gitubuntu/clone.py
index f34b453..4da8d4a 100644
--- a/gitubuntu/clone.py
+++ b/gitubuntu/clone.py
@@ -99,8 +99,9 @@ def main(
 
     try:
         local_repo.create_tracking_branch(
-            'ubuntu/devel',
-            'pkg/ubuntu/devel'
+            local_branch_name='ubuntu/devel',
+            remote_name='pkg',
+            remote_branch_name='ubuntu/devel',
         )
         local_repo.checkout_commitish('ubuntu/devel')
     except:
diff --git a/gitubuntu/git_repository.py b/gitubuntu/git_repository.py
index 27ed645..e57dc1d 100644
--- a/gitubuntu/git_repository.py
+++ b/gitubuntu/git_repository.py
@@ -2189,15 +2189,38 @@ class GitUbuntuRepository:
         _, _, pretty_name = tag.name.partition('refs/tags/')
         return pretty_name
 
-    def create_tracking_branch(self, branch_name, upstream_name, force=False):
-        return self.raw_repo.create_branch(
-            branch_name,
+    def create_tracking_branch(
+        self,
+        local_branch_name,
+        remote_name,
+        remote_branch_name,
+        force=False,
+    ):
+        """Create a local branch that tracks a remote branch
+
+        The remote tracking branch ("refs/remotes/...") must already exist.
+        Usually this means that "git fetch" must have been run to create it.
+
+        :param str local_branch_name: the name of the local branch to create
+        :param str remote_name: the name of the remote
+        :param str remote_branch_name: the name of the remote branch
+        :param bool force: overwrite existing branch
+        :rtype: pygit2.Branch
+        :returns: the newly created branch
+        """
+        branch = self.raw_repo.create_branch(
+            local_branch_name,
             self.raw_repo.lookup_branch(
-                upstream_name,
-                pygit2.GIT_BRANCH_REMOTE
+                f'{remote_name}/{remote_branch_name}',
+                pygit2.GIT_BRANCH_REMOTE,
             ).peel(pygit2.Commit),
             force
         )
+        remote_config = f'branch.{local_branch_name}.remote'
+        branch_config = f'branch.{local_branch_name}.merge'
+        self.raw_repo.config[remote_config] = remote_name
+        self.raw_repo.config[branch_config] = f'refs/heads/{local_branch_name}'
+        return branch
 
     def checkout_commitish(self, commitish):
         # pygit2 checkout does not accept hashes
diff --git a/gitubuntu/git_repository_test.py b/gitubuntu/git_repository_test.py
index 05bc157..d0bc4fd 100644
--- a/gitubuntu/git_repository_test.py
+++ b/gitubuntu/git_repository_test.py
@@ -1197,3 +1197,61 @@ def test_get_head_info(repo):
             commit_id=foo_commit_id,
         ),
     }
+
+
+def test_create_tracking_branch(repo, pygit2_repo):
+    """
+    :param GitUbuntuRepository repo: fixture providing a temporary
+        GitUbuntuRepository instance to use
+    :param pygit2.Repository pygit2_repo: fixture providing a temporary
+        pygit2.Repository instance to use
+    """
+    # Note that we cannot use a repo instance twice, because pytest will give
+    # us only one instance. A convenient workaround is that the remote repo
+    # doesn't need to be a GitUbuntuRepository and so the pygit2_repo fixture
+    # will do as it is independent. We can assert they are definitely
+    # different:
+    assert repo.raw_repo is not pygit2_repo
+    Repo(
+        commits=[Commit(name='main')],
+        branches={'main': Placeholder('main')},
+    ).write(pygit2_repo)
+    repo.raw_repo.remotes.create('origin', pygit2_repo.path)
+    repo.git_run(['fetch', 'origin', 'main'])
+    repo.create_tracking_branch(
+        local_branch_name='main',
+        remote_name='origin',
+        remote_branch_name='main',
+    )
+    assert (
+        repo.raw_repo.references['refs/heads/main'].peel(pygit2.Commit).id
+        == pygit2_repo.references['refs/heads/main'].peel(pygit2.Commit).id
+    )
+
+
+def test_create_tracking_branch_tracks(repo, pygit2_repo):
+    """
+    :param GitUbuntuRepository repo: fixture providing a temporary
+        GitUbuntuRepository instance to use
+    :param pygit2.Repository pygit2_repo: fixture providing a temporary
+        pygit2.Repository instance to use
+    """
+    # Note that we cannot use a repo instance twice, because pytest will give
+    # us only one instance. A convenient workaround is that the remote repo
+    # doesn't need to be a GitUbuntuRepository and so the pygit2_repo fixture
+    # will do as it is independent. We can assert they are definitely
+    # different:
+    assert repo.raw_repo is not pygit2_repo
+    Repo(
+        commits=[Commit(name='main')],
+        branches={'main': Placeholder('main')},
+    ).write(pygit2_repo)
+    repo.raw_repo.remotes.create('origin', pygit2_repo.path)
+    repo.git_run(['fetch', 'origin', 'main'])
+    repo.create_tracking_branch(
+        local_branch_name='main',
+        remote_name='origin',
+        remote_branch_name='main',
+    )
+    assert repo.raw_repo.config['branch.main.remote'] == 'origin'
+    assert repo.raw_repo.config['branch.main.merge'] == 'refs/heads/main'
diff --git a/gitubuntu/merge.py b/gitubuntu/merge.py
index 27678c4..f0ee681 100644
--- a/gitubuntu/merge.py
+++ b/gitubuntu/merge.py
@@ -418,8 +418,9 @@ def main(
         )
         try:
             branch = repo.create_tracking_branch(
-                onto,
-                'pkg/%s' % onto,
+                local_branch_name=onto,
+                remote_name='pkg',
+                remote_branch_name=onto,
                 force=force,
             )
         except: