Merge branch 'jc/branch-previous'

* jc/branch-previous:
  Teach @{-1} to git merge
  Teach the "@{-1} syntax to "git branch"

t/t0100-previous.sh

@@ -0,0 +1,49 @@
+#!/bin/sh
+
+test_description='previous branch syntax @{-n}'
+
+. ./test-lib.sh
+
+test_expect_success 'branch -d @{-1}' '
+	test_commit A &&
+	git checkout -b junk &&
+	git checkout - &&
+	test "$(git symbolic-ref HEAD)" = refs/heads/master &&
+	git branch -d @{-1} &&
+	test_must_fail git rev-parse --verify refs/heads/junk
+'
+
+test_expect_success 'branch -d @{-12} when there is not enough switches yet' '
+	git reflog expire --expire=now &&
+	git checkout -b junk2 &&
+	git checkout - &&
+	test "$(git symbolic-ref HEAD)" = refs/heads/master &&
+	test_must_fail git branch -d @{-12} &&
+	git rev-parse --verify refs/heads/master
+'
+
+test_expect_success 'merge @{-1}' '
+	git checkout A &&
+	test_commit B &&
+	git checkout A &&
+	test_commit C &&
+	git branch -f master B &&
+	git branch -f other &&
+	git checkout other &&
+	git checkout master &&
+	git merge @{-1} &&
+	git cat-file commit HEAD | grep "Merge branch '\''other'\''"
+'
+
+test_expect_success 'merge @{-1} when there is not enough switches yet' '
+	git reflog expire --expire=now &&
+	git checkout -f master &&
+	git reset --hard B &&
+	git branch -f other C &&
+	git checkout other &&
+	git checkout master &&
+	test_must_fail git merge @{-12}
+'
+
+test_done
+