From 38062e2d973373415af93bec4bd99f5ecd58b5db Mon Sep 17 00:00:00 2001
From: Pierre-Yves Chibon <pingou@pingoured.fr>
Date: Mar 23 2017 10:14:34 +0000
Subject: Optimize diffing pull-requests


Instead of listing all the commits in one branch then going through the
second to find the common commits, we iterate through both branches at
the same time and stop when there is an overlap in both lists.

---

diff --git a/pagure/lib/git.py b/pagure/lib/git.py
index d881301..abca818 100644
--- a/pagure/lib/git.py
+++ b/pagure/lib/git.py
@@ -1365,17 +1365,30 @@ def diff_pull_request(
             'seems to no longer be present in this repo' % request.branch)
 
     if not repo_obj.is_empty and not orig_repo.is_empty:
-        # Pull-request open
-        master_commits = [
-            commit.oid.hex
-            for commit in orig_repo.walk(
-                orig_repo.lookup_branch(request.branch).get_object().hex,
-                pygit2.GIT_SORT_TIME)
-        ]
-        for commit in repo_obj.walk(commitid, pygit2.GIT_SORT_TIME):
-            if request.status and commit.oid.hex in master_commits:
+
+        main_walker = repo_obj.walk(
+            orig_repo.lookup_branch(request.branch).get_object().hex,
+            pygit2.GIT_SORT_TIME)
+        branch_walker = repo_obj.walk(commitid, pygit2.GIT_SORT_TIME)
+        main_commits = set()
+        branch_commits = set()
+
+        while 1:
+            try:
+                com = main_walker.next()
+                main_commits.add(com.hex)
+            except StopIteration:
+                pass
+            try:
+                branch_commit = branch_walker.next()
+            except StopIteration:
+                branch_commit = None
+
+            branch_commits.add(branch_commit.oid.hex)
+            if main_commits.intersection(branch_commits):
                 break
-            diff_commits.append(commit)
+
+            diff_commits.append(branch_commit)
 
         if request.status and diff_commits:
             first_commit = repo_obj[diff_commits[-1].oid.hex]