Cleanup: Refactor BKE_nlatrack_add to multiple methods to handle adding a new NLA track to the track list. Insert before, after, head, and tail

@@ -37,1 +37,4 @@
 
+/**
+ * Create new NLA Track.
+ */

@@ -93,0 +130,4 @@
+ * Calls #BKE_nlatrack_new to create a new NLA track, inserts it as the head of the
+ * NLA track list with #BKE_nlatrack_new_before_and_set_active, and sets it as active.
+ */
+struct NlaTrack *BKE_nlatrack_new_head_and_set_active(ListBase *nla_tracks, bool is_liboverride);

@@ -354,0 +354,4 @@
+{
+  if (is_liboverride) {
+
+    /** Currently, all library override tracks are assumed to be grouped together at the start of

@@ -354,0 +360,4 @@
+      BKE_nlatrack_insert_after(nla_tracks, next, new_track, is_liboverride);
+      return;
+    }
+  }

@@ -354,0 +381,4 @@
+                               struct NlaTrack *new_track,
+                               bool is_liboverride)
+{
+  BLI_assert(!ELEM(NULL, nla_tracks, new_track));

@@ -116,4 +114,38 @@ TEST(nla_track, BKE_nlatrack_remove_and_free)
   EXPECT_EQ(-1, BLI_findindex(&adt.nla_tracks, track1));
 }
 
+TEST(nla_track, BKE_nlatrack_new_tail_and_set_active)

@@ -576,1 +576,3 @@
-  NlaTrack *new_track = BKE_nlatrack_add(adt, track, ID_IS_OVERRIDE_LIBRARY(id));
+  NlaTrack *new_track;
+
+  if (track != NULL) {

@@ -93,0 +113,4 @@
+
+/**
+ * Calls #BKE_nlatrack_new to create a new NLA track, inserts it before the
+ * given NLA track with #BKE_nlatrack_insert_before, and sets it as active.