remove a TODO that turned out to be unnecessary.

After all, stopping the merge when there is any conflict is highly relevant.

Author: Byron

README.md

@@ -46,7 +46,7 @@ What follows is a high-level list of features and those which are planned:
 * [x] blob-diff
 * [ ] merge
     - [x] blobs
-    - [ ] trees
+    - [x] trees
     - [ ] commits
 * [ ] rebase
 * [ ] commit

gix-merge/src/tree/mod.rs

@@ -236,11 +236,8 @@ pub struct Options {
     /// The context to use when invoking merge-drivers.
     pub blob_merge_command_ctx: gix_command::Context,
     /// If `Some(what-is-unresolved)`, the first unresolved conflict will cause the entire merge to stop.
-    /// This is useful to see if there is any conflict, without performing the whole operation.
-    // TODO: Maybe remove this if the cost of figuring out conflicts is so low - after all, the data structures
-    //       and initial diff is the expensive thing right now, which are always done upfront.
-    //       However, this could change once we know do everything during the traversal, which probably doesn't work
-    //       without caching stuff and is too complicated to actually do.
+    /// This is useful to see if there is any conflict, without performing the whole operation, something
+    /// that can be very relevant during merges that would cause a lot of blob-diffs.
     pub fail_on_conflict: Option<UnresolvedConflict>,
     /// This value also affects the size of merge-conflict markers, to allow differentiating
     /// merge conflicts on each level, for any value greater than 0, with values `N` causing `N*2`

gix/src/repository/merge.rs

@@ -111,6 +111,11 @@ impl Repository {
     /// `labels` are typically chosen to identify the refs or names for `our_tree` and `their_tree` and `ancestor_tree` respectively.
     ///
     /// `options` should be initialized with [`tree_merge_options()`](Self::tree_merge_options()).
+    ///
+    /// ### Performance
+    ///
+    /// It's highly recommended to [set an object cache](crate::Repository::compute_object_cache_size_for_tree_diffs)
+    /// to avoid extracting the same object multiple times.
     // TODO: Use `crate::merge::Options` here and add niceties such as setting the resolution strategy.
     pub fn merge_trees(
         &self,