From c3ab08844c30f85342622fef1e4cf1ef1bb2bcd0 Mon Sep 17 00:00:00 2001
From: Joachim Kuebart <joachim.kuebart@gmail.com>
Date: Wed, 5 May 2021 11:56:25 +0000
Subject: git-p4: ensure complex branches are cloned correctly

When importing a branch from p4, git-p4 searches the history of the parent
branch for the branch point. The test for the complex branch structure
ensures all files have the expected contents, but doesn't examine the
branch structure.

Check for the correct branch structure by making sure that the initial
commit on each branch is empty. This ensures that the initial commit's
parent is indeed the correct branch-off point.

Signed-off-by: Joachim Kuebart <joachim.kuebart@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t9801-git-p4-branch.sh b/t/t9801-git-p4-branch.sh
index 56e6469..0d3520f 100755
--- a/t/t9801-git-p4-branch.sh
+++ b/t/t9801-git-p4-branch.sh
@@ -294,11 +294,13 @@ test_expect_success 'git p4 clone complex branches' '
 		test_path_is_file file3 &&
 		grep update file2 &&
 		git reset --hard p4/depot/branch4 &&
+		git diff-tree --quiet HEAD &&
 		test_path_is_file file1 &&
 		test_path_is_file file2 &&
 		test_path_is_missing file3 &&
 		! grep update file2 &&
 		git reset --hard p4/depot/branch5 &&
+		git diff-tree --quiet HEAD &&
 		test_path_is_file file1 &&
 		test_path_is_file file2 &&
 		test_path_is_file file3 &&
-- 
cgit v0.10.2-6-g49f6


From 6b79818bfbd39a5d41d15003375a9f382f70ad0e Mon Sep 17 00:00:00 2001
From: Joachim Kuebart <joachim.kuebart@gmail.com>
Date: Wed, 5 May 2021 11:56:26 +0000
Subject: git-p4: speed up search for branch parent

For every new branch that git-p4 imports, it needs to find the commit
where it branched off its parent branch. While p4 doesn't record this
information explicitly, the first changelist on a branch is usually an
identical copy of the parent branch.

The method searchParent() tries to find a commit in the history of the
given "parent" branch whose tree exactly matches the initial changelist
of the new branch, "target". The code iterates through the parent
commits and compares each of them to this initial changelist using
diff-tree.

Since we already know the tree object name we are looking for, spawning
diff-tree for each commit is wasteful.

Use the "--format" option of "rev-list" to find out the tree object name
of each commit in the history, and find the tree whose name is exactly
the same as the tree of the target commit to optimize this.

This results in a considerable speed-up, at least on Windows. On one
Windows machine with a fairly large repository of about 16000 commits in
the parent branch, the current code takes over 7 minutes, while the new
code only takes just over 10 seconds for the same changelist:

Before:

    $ time git p4 sync
    Importing from/into multiple branches
    Depot paths: //depot
    Importing revision 31274 (100.0%)
    Updated branches: b1

    real    7m41.458s
    user    0m0.000s
    sys     0m0.077s

After:

    $ time git p4 sync
    Importing from/into multiple branches
    Depot paths: //depot
    Importing revision 31274 (100.0%)
    Updated branches: b1

    real    0m10.235s
    user    0m0.000s
    sys     0m0.062s

Signed-off-by: Joachim Kuebart <joachim.kuebart@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-p4.py b/git-p4.py
index 09c9e93..d34a194 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -3600,19 +3600,18 @@ class P4Sync(Command, P4UserMap):
         return True
 
     def searchParent(self, parent, branch, target):
-        parentFound = False
-        for blob in read_pipe_lines(["git", "rev-list", "--reverse",
+        targetTree = read_pipe(["git", "rev-parse",
+                                "{}^{{tree}}".format(target)]).strip()
+        for line in read_pipe_lines(["git", "rev-list", "--format=%H %T",
                                      "--no-merges", parent]):
-            blob = blob.strip()
-            if len(read_pipe(["git", "diff-tree", blob, target])) == 0:
-                parentFound = True
+            if line.startswith("commit "):
+                continue
+            commit, tree = line.strip().split(" ")
+            if tree == targetTree:
                 if self.verbose:
-                    print("Found parent of %s in commit %s" % (branch, blob))
-                break
-        if parentFound:
-            return blob
-        else:
-            return None
+                    print("Found parent of %s in commit %s" % (branch, commit))
+                return commit
+        return None
 
     def importChanges(self, changes, origin_revision=0):
         cnt = 1
-- 
cgit v0.10.2-6-g49f6