fix: Repository::tree_merge_options() now comes with rewrite tracking.

This is the way Git acts, as it's either configured, or defaults to the value
coming from the `diff.renames` configuration.

Author: Byron

gix/src/diff.rs

@@ -175,7 +175,7 @@ pub(crate) mod utils {
         new_rewrites_inner(config, lenient, &Diff::RENAMES, &Diff::RENAME_LIMIT)
     }
 
-    pub fn new_rewrites_inner(
+    pub(crate) fn new_rewrites_inner(
         config: &gix_config::File<'static>,
         lenient: bool,
         renames: &'static crate::config::tree::diff::Renames,

gix/src/repository/merge.rs

@@ -94,7 +94,12 @@ impl Repository {
                 self.config.lenient_config,
                 &tree::Merge::RENAMES,
                 &tree::Merge::RENAME_LIMIT,
-            )?,
+            )?
+            .map(Ok)
+            .or_else(|| crate::diff::utils::new_rewrites(&self.config.resolved, self.config.lenient_config).transpose())
+            .transpose()?
+            .unwrap_or_default()
+            .into(),
             blob_merge: self.blob_merge_options()?,
             blob_merge_command_ctx: self.command_context()?,
             fail_on_conflict: None,