Merge branch 'jk/maint-1.6.3-checkout-unborn' into maint

* jk/maint-1.6.3-checkout-unborn:
  checkout: do not imply "-f" on unborn branches

t/t2015-checkout-unborn.sh

@@ -0,0 +1,40 @@
+#!/bin/sh
+
+test_description='checkout from unborn branch protects contents'
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	mkdir parent &&
+	(cd parent &&
+	 git init &&
+	 echo content >file &&
+	 git add file &&
+	 git commit -m base
+	) &&
+	git fetch parent master:origin
+'
+
+test_expect_success 'checkout from unborn preserves untracked files' '
+	echo precious >expect &&
+	echo precious >file &&
+	test_must_fail git checkout -b new origin &&
+	test_cmp expect file
+'
+
+test_expect_success 'checkout from unborn preserves index contents' '
+	echo precious >expect &&
+	echo precious >file &&
+	git add file &&
+	test_must_fail git checkout -b new origin &&
+	test_cmp expect file &&
+	git show :file >file &&
+	test_cmp expect file
+'
+
+test_expect_success 'checkout from unborn merges identical index contents' '
+	echo content >file &&
+	git add file &&
+	git checkout -b new origin
+'
+
+test_done