Customizing similarity index for renamed files

[jakubbortlik]

In gitlab.nvim we are using diffview.nvim as the "reviewer" for Gitlab merge requests. I've noticed that Gitlab must be using a non-default threshold for similarity index for finding renames (git docs), I've got a file that was renamed and modified and Gitlab shows it as such, while Diffview shows the original file as deleted and a new file added. This is because the similarity index for the given file was 41, so I'm able to force Diffview into the same behaviour as Gitlab with this modification:

diff --git a/lua/diffview/vcs/adapters/git/init.lua b/lua/diffview/vcs/adapters/git/init.lua
index 3a137bc..65ff4a3 100644
--- a/lua/diffview/vcs/adapters/git/init.lua
+++ b/lua/diffview/vcs/adapters/git/init.lua
@@ -1707,6 +1707,7 @@ GitAdapter.tracked_files = async.wrap(function(self, left, right, args, kind, op
       "-c",
       "core.quotePath=false",
       "diff",
+      "-M40%",
       "--ignore-submodules",
       "--name-status",
       args
@@ -1721,6 +1722,7 @@ GitAdapter.tracked_files = async.wrap(function(self, left, right, args, kind, op
       "-c",
       "core.quotePath=false",
       "diff",
+      "-M40%",
       "--ignore-submodules",
       "--numstat",
       args

It would be nice if this option to Git would be configurable in Diffview, so that we could make gitlab.nvim behave as close to Gitlab as possible.

Note: There's already the possibility to configure the git_cmd in Diffview, but obviously, this cannot be set to something like git_cmd = {"git", "-M40%"}, because the -M40% option only makes sense for the diff subcommand.