Merge ~cjwatson/launchpad:stricter-branch-getByPath into launchpad:master

[Colin Watson]

Make BranchSet.getByPath forbid paths with suffixes

It previously accepted suffixes and discarded them. This stricter approach is consistent with how `GitRepositorySet.getByPath` works, and it makes things easier for Breezy (which already walks up the path structure until it finds a match, but we were deceiving it by returning inexact matches). It's also a better match to the existing API documentation, which didn't mention anything about accepting suffixes.

[Jelmer Vernooij (jelmer)]

Thanks for the quick fix!

review: Approve

[Otto Co-Pilot (otto-copilot)]

Voting criteria not met
https://jenkins.ols.canonical.com/online-services/job/launchpad/3059/

[Colin Watson (cjwatson)]

Working around voting restrictions (I'm happy with Jelmer's review as being sufficient on this).

review: Approve

diff --git a/lib/lp/code/model/branchlookup.py b/lib/lp/code/model/branchlookup.py
index 8888a0f..5c40120 100644
--- a/lib/lp/code/model/branchlookup.py
+++ b/lib/lp/code/model/branchlookup.py
@@ -410,7 +410,7 @@ class BranchLookup:
     def getByPath(self, path):
         """See `IBranchLookup`."""
         try:
-            return self.getByLPPath(path)[0]
+            branch, suffix = self.getByLPPath(path)
         except (
             CannotHaveLinkedBranch,
             InvalidNamespace,
@@ -424,6 +424,9 @@ class BranchLookup:
             NoLinkedBranch,
         ):
             return None
+        if suffix:
+            return None
+        return branch
 
     def _getLinkedBranchAndPath(self, provided):
         """Get the linked branch for 'provided', and the bzr_path.
diff --git a/lib/lp/code/model/tests/test_branchlookup.py b/lib/lp/code/model/tests/test_branchlookup.py
index 206e540..6cf90c1 100644
--- a/lib/lp/code/model/tests/test_branchlookup.py
+++ b/lib/lp/code/model/tests/test_branchlookup.py
@@ -268,7 +268,10 @@ class TestGetByPath(TestGetByLPPath):
         self.assertIsNone(self.getByPath(path))
 
     def assertPath(self, expected_branch, expected_suffix, path):
-        self.assertEqual(expected_branch, self.getByPath(path))
+        if expected_suffix:
+            self.assertIsNone(self.getByPath(path))
+        else:
+            self.assertEqual(expected_branch, self.getByPath(path))
 
 
 class TestGetByUrl(TestCaseWithFactory):