1 files changed, 83 insertions, 0 deletions
diff --git a/buildstream/testing/_utils/junction.py b/buildstream/testing/_utils/junction.py
new file mode 100644
index 000000000..ca059eb8b
--- /dev/null
+++ b/buildstream/testing/_utils/junction.py
@@ -0,0 +1,83 @@
+import subprocess
+import pytest
+
+from buildstream import _yaml
+from .. import Repo
+from .site import HAVE_GIT, GIT, GIT_ENV
+
+
+# generate_junction()
+#
+# Generates a junction element with a git repository
+#
+# Args:
+#    tmpdir: The tmpdir fixture, for storing the generated git repo
+#    subproject_path: The path for the subproject, to add to the git repo
+#    junction_path: The location to store the generated junction element
+#    store_ref: Whether to store the ref in the junction.bst file
+#
+# Returns:
+#    (str): The ref
+#
+def generate_junction(tmpdir, subproject_path, junction_path, *, store_ref=True):
+    # Create a repo to hold the subproject and generate
+    # a junction element for it
+    #
+    repo = _SimpleGit(str(tmpdir))
+    source_ref = ref = repo.create(subproject_path)
+    if not store_ref:
+        source_ref = None
+
+    element = {
+        'kind': 'junction',
+        'sources': [
+            repo.source_config(ref=source_ref)
+        ]
+    }
+    _yaml.dump(element, junction_path)
+
+    return ref
+
+
+# A barebones Git Repo class to use for generating junctions
+class _SimpleGit(Repo):
+    def __init__(self, directory, subdir='repo'):
+        if not HAVE_GIT:
+            pytest.skip('git is not available')
+        super().__init__(directory, subdir)
+
+    def create(self, directory):
+        self.copy_directory(directory, self.repo)
+        self._run_git('init', '.')
+        self._run_git('add', '.')
+        self._run_git('commit', '-m', 'Initial commit')
+        return self.latest_commit()
+
+    def latest_commit(self):
+        return self._run_git(
+            'rev-parse', 'HEAD',
+            stdout=subprocess.PIPE,
+            universal_newlines=True,
+        ).stdout.strip()
+
+    def source_config(self, ref=None, checkout_submodules=None):
+        config = {
+            'kind': 'git',
+            'url': 'file://' + self.repo,
+            'track': 'master'
+        }
+        if ref is not None:
+            config['ref'] = ref
+        if checkout_submodules is not None:
+            config['checkout-submodules'] = checkout_submodules
+
+        return config
+
+    def _run_git(self, *args, **kwargs):
+        argv = [GIT]
+        argv.extend(args)
+        if 'env' not in kwargs:
+            kwargs['env'] = dict(GIT_ENV, PWD=self.repo)
+        kwargs.setdefault('cwd', self.repo)
+        kwargs.setdefault('check', True)
+        return subprocess.run(argv, **kwargs)