Merge "Handle explicit merges"

git_upstream/lib/searchers.py

@@ -128,7 +128,9 @@ class Searcher(GitMixin):
             self.log.debug("Merge base is not the same as root merge base")
             return None, [], None
 
-        other_parents = [p.hexsha for p in mergecommit.parents if p != parent]
+        other_parents = set(
+            p.hexsha for p in mergecommit.parents if p != parent
+        )
         self.log.debug("Merge base is same: other_parents: %s", other_parents)
 
         # if the merge base of the parent against any of the other parents
@@ -145,6 +147,11 @@ class Searcher(GitMixin):
         if exclude_commits:
             return None, [], exclude_commits
 
+        # handle case where merges are always created in GitHub even when
+        # not needed.
+        if other_parents.issubset(ancestry_commits):
+            return None, [], []
+
         # otherwise looking at the previous import merge commit and the parent
         # from the previous import branch, so exclude all other parents.
         return mergecommit, ["^%s" % ip for ip in other_parents], None

git_upstream/tests/searchers/scenarios/explict-merge-treesame.yaml

@@ -0,0 +1,37 @@
+- desc: |
+    Construct a repo layout where using a complex layout where no
+    previous import from upstream having been completed, test that if a
+    change has been explicitly merged (common with GitHub PR's) without
+    it being necessary, then the searcher will correct include the
+    change and not detect it as a possible import merge
+
+    will the searcher correctly include 'O' below even though there was
+    no need for a merge 'D' to be created.
+
+    Repository layout being tested
+
+            O
+           / \
+      B---C---D---G                     master
+     /
+    A---E---F---L---M                   upstream/master
+
+
+  tree:
+    - [A, []]
+    - [B, [A]]
+    - [C, [B]]
+    - [O, [C]]
+    - [D, [C, =O]]
+    - [E, [A]]
+    - [F, [E]]
+    - [G, [D]]
+    - [L, [F]]
+    - [M, [L]]
+
+  branches:
+    head: [master, G]
+    upstream: [upstream/master, M]
+
+  expected-changes: [B, C, O, D, G]
+