Simplify logic in StrategySimpleTwoWayInCore

Sasa and I were reviewing this code today and Sasa pointed out we
can simplify the conflict logic, as the two cases (subtree and file)
are logically identical.

Change-Id: Ie0d40b2dd15605785eff453a846b1d20a2d021fc
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Reviewed-by: Sasa Zivkov <zivkov@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/merge/StrategySimpleTwoWayInCore.java

 					add(T_THEIRS, DirCacheEntry.STAGE_0);
 				else if (modeB == modeT && tw.idEqual(T_BASE, T_THEIRS))
 					add(T_OURS, DirCacheEntry.STAGE_0);
-				else if (tw.isSubtree()) {
+				else {
 					if (nonTree(modeB)) {
 						add(T_BASE, DirCacheEntry.STAGE_1);
 						hasConflict = true;
 						add(T_THEIRS, DirCacheEntry.STAGE_3);
 						hasConflict = true;
 					}
-					tw.enterSubtree();
-				} else {
-					add(T_BASE, DirCacheEntry.STAGE_1);
-					add(T_OURS, DirCacheEntry.STAGE_2);
-					add(T_THEIRS, DirCacheEntry.STAGE_3);
-					hasConflict = true;
+					if (tw.isSubtree())
+						tw.enterSubtree();
 				}
 			}
 			builder.finish();