Add test case for LineNumberOfLine()

There's a bug in LineNumberOfLine, but the existing test coverage doesn't catch
it, as the only test case for this was one where oldStart and newStart were the
same for all hunks. Add a test case where newStart is different for one of the
hunks; this demonstrates a bug, where all expected results from index 12 on are
off by one.

pkg/commands/patch/patch_test.go

@@ -67,6 +67,29 @@ index e48a11c..b2ab81b 100644
  ...
 `
 
+const twoHunksWithMoreAdditionsThanRemovals = `diff --git a/filename b/filename
+index bac359d75..6e5b89f36 100644
+--- a/filename
++++ b/filename
+@@ -1,5 +1,6 @@
+ apple
+-grape
++orange
++kiwi
+ ...
+ ...
+ ...
+@@ -8,6 +9,8 @@ grape
+ ...
+ ...
+ ...
++pear
++lemon
+ ...
+ ...
+ ...
+`
+
 const twoChangesInOneHunk = `diff --git a/filename b/filename
 index 9320895..6d79956 100644
 --- a/filename
@@ -572,6 +595,12 @@ func TestLineNumberOfLine(t *testing.T) {
 			indexes:   []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 1000},
 			expecteds: []int{1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 5, 8, 8, 9, 10, 11, 12, 13, 14, 15, 15, 15, 15, 15, 15},
 		},
+		{
+			testName:  "twoHunksWithMoreAdditionsThanRemovals",
+			patchStr:  twoHunksWithMoreAdditionsThanRemovals,
+			indexes:   []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 1000},
+			expecteds: []int{1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 5, 6, 8, 8, 9, 10, 11, 12, 13, 14, 15, 16, 16, 16, 16, 16},
+		},
 	}
 
 	for _, s := range scenarios {