sha1_name: support @{-N} syntax in get_sha1()

Let get_sha1() parse the @{-N} syntax, with docs and tests.

Note that while @{-1}^2, @{-2}~5 and such are supported, @{-1}@{1} is
currently not allowed.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/t/t1505-rev-parse-last.sh b/t/t1505-rev-parse-last.sh
new file mode 100755
index 000000000..1e49dd2c8
--- /dev/null
+++ b/t/t1505-rev-parse-last.sh
@@ -0,0 +1,71 @@
+#!/bin/sh
+
+test_description='test @{-N} syntax'
+
+. ./test-lib.sh
+
+
+make_commit () {
+	echo "$1" > "$1" &&
+	git add "$1" &&
+	git commit -m "$1"
+}
+
+
+test_expect_success 'setup' '
+
+	make_commit 1 &&
+	git branch side &&
+	make_commit 2 &&
+	make_commit 3 &&
+	git checkout side &&
+	make_commit 4 &&
+	git merge master &&
+	git checkout master
+
+'
+
+# 1 -- 2 -- 3 master
+#  \         \
+#   \         \
+#    --- 4 --- 5 side
+#
+# and 'side' should be the last branch
+
+git log --graph --all --pretty=oneline --decorate
+
+test_rev_equivalent () {
+
+	git rev-parse "$1" > expect &&
+	git rev-parse "$2" > output &&
+	test_cmp expect output
+
+}
+
+test_expect_success '@{-1} works' '
+	test_rev_equivalent side @{-1}
+'
+
+test_expect_success '@{-1}~2 works' '
+	test_rev_equivalent side~2 @{-1}~2
+'
+
+test_expect_success '@{-1}^2 works' '
+	test_rev_equivalent side^2 @{-1}^2
+'
+
+test_expect_failure '@{-1}@{1} works' '
+	test_rev_equivalent side@{1} @{-1}@{1}
+'
+
+test_expect_success '@{-2} works' '
+	test_rev_equivalent master @{-2}
+'
+
+test_expect_success '@{-3} fails' '
+	test_must_fail git rev-parse @{-3}
+'
+
+test_done
+
+