OutOfMemory Error with Repository.Diff.Compare<Patch>(...)

Start by tracing the reported call path through Core/Ensure.cs, Core/Proxy.cs, PatchStats.cs, and Diff.cs, then review the linked Stack Overflow discussion. Reproduce the failure with Repository.Diff.Compare on a repository with comparable commit history and determine which operation retains excessive memory. Done means the comparison completes without the reported OutOfMemoryException and regression coverage is added for the failing case.

I get an OutOfMemoryException from Repository.Diff with v0.22.0:

LibGit2Sharp.LibGit2SharpException: Out of memory
   at LibGit2Sharp.Core.Ensure.HandleError(Int32 result) in c:\Git\libgit2sharp\LibGit2Sharp\Core\Ensure.cs:line 160
   at LibGit2Sharp.Core.Proxy.git_patch_from_diff(DiffSafeHandle diff, Int32 idx) in c:\Git\libgit2sharp\LibGit2Sharp\Core\Proxy.cs:line 1555
   at LibGit2Sharp.PatchStats..ctor(DiffSafeHandle diff) in c:\Git\libgit2sharp\LibGit2Sharp\PatchStats.cs:line 31
   at LibGit2Sharp.Diff.<.cctor>b__1d(DiffSafeHandle diff) in c:\Git\libgit2sharp\LibGit2Sharp\Diff.cs:line 106
   at LibGit2Sharp.Diff.BuildDiffResult[T](DiffSafeHandle diff) in c:\Git\libgit2sharp\LibGit2Sharp\Diff.cs:line 120
   at LibGit2Sharp.Diff.Compare[T](Tree oldTree, Tree newTree, IEnumerable`1 paths, ExplicitPathsOptions explicitPathsOptions, CompareOptions compareOptions) in c:\Git\libgit2sharp\LibGit2Sharp\Diff.cs:line 246
   at LibGit2Sharp.Diff.Compare[T](Tree oldTree, Tree newTree) in c:\Git\libgit2sharp\LibGit2Sharp\Diff.cs:line 157
   at ABB.QueryManager.Models.Git.GitCodeChurnToCsvConverter.<GetRowData>d__7.MoveNext() in C:\Workspace\Source\TeamMetrics\QueryManager\QueryManager\Models\Git\GitCodeChurnToCsvConverter.cs:line 52

I'm trying to produce some basic code churn statistics from a Git repository. As some context, I'm implementing this in an ASP.NET application in a Hangfire job.

For each branch, I'm iterating over all of the commits and comparing them to their predecessor. I generate a patch per commit, and generate data for each file path in the commit. Here is the code I'm using:

foreach (var branch in repo.Branches.Where(b => b.Tip.Committer.When >= startDate))
{
	Commit nextCommit = null;
	foreach (var currentCommit in branch.Commits.Where(c => c.Committer.When >= startDate))
	{
		if(null == nextCommit)
		{
			foreach (var change in repo.Diff.Compare<Patch>(currentCommit.Tree, nextCommit.Tree))
			{
				var data = new string[]
				{
					nextCommit.Id.Sha,
					branch.FriendlyName,
					change.Path,
					change.Status.ToString(),
					change.IsBinaryComparison.ToString(),
					GetFileSize(nextCommit, change.Path).ToString(),
					GetLineCount(nextCommit, change.Path).ToString(),
					change.LinesAdded.ToString(),
					change.LinesDeleted.ToString()
				}
				yield return data;
			}
		}
		nextCommit = currentCommit;
	}
}

I found this related Stack Overflow question: libgit2sharp.Patch outofmemory. I tried changing my code to produce both a TreeChanges and a PatchStats, but it fails as well.