Fix issue with the git log

The old code was assuming that the buffer was not going to change, this is not
true with the current impl though where the list is shifted and ybase and ydisp
need to be compensated for that.

src/utils/CircularList.ts

@@ -84,12 +84,16 @@ export class CircularList<T> {
     this._array[this._getCyclicIndex(this._length)] = value;
     if (this._length === this.maxLength) {
       this._startIndex++;
+      if (this._startIndex === this.maxLength) {
+        this._startIndex = 0;
+      }
     } else {
       this._length++;
     }
   }
 
   public pop(): T {
+    // TODO: This isn't popping from the array, only returning
     return this._array[this._getCyclicIndex(this._length-- - 1)];
   }
 
@@ -118,6 +122,13 @@ export class CircularList<T> {
     }
   }
 
+  public trimStart(count: number): void {
+    // TODO: Error handling
+    // TODO: Testing (if we need this)
+    this._startIndex += count;
+    this._length--;
+  }
+
   private _getCyclicIndex(index: number): number {
     return (this._startIndex + index) % this.maxLength;
   }