[PATCH 2/2 v3] sha1_name: teach get_sha1_1 "-" shorthand for "@{-1}"

[Siddharth Kannan <kannan.siddharth12@gmail.com>]

This patch introduces "-" as a method to refer to a revision, and adds tests to
test that git-log works with this shorthand.

This change will touch the following commands (through
revision.c:setup_revisions):

* builtin/blame.c
* builtin/diff.c
* builtin/diff-files.c
* builtin/diff-index.c
* builtin/diff-tree.c
* builtin/log.c
* builtin/rev-list.c
* builtin/shortlog.c
* builtin/fast-export.c
* builtin/fmt-merge-msg.c
builtin/add.c
builtin/checkout.c
builtin/commit.c
builtin/merge.c
builtin/pack-objects.c
builtin/revert.c

* marked commands are information-only.

As most commands in this list are not of the rm-variety, (i.e a command that
would delete something), this change does not make it easier for people to
delete. (eg: "git branch -d -" is *not* enabled by this patch)

Signed-off-by: Siddharth Kannan <kannan.siddharth12@gmail.com>
---
 sha1_name.c              |  5 ++++
 t/t4214-log-shorthand.sh | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100755 t/t4214-log-shorthand.sh

diff --git a/sha1_name.c b/sha1_name.c
index 73a915f..d774e46 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -947,6 +947,11 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
 	if (!ret)
 		return 0;
 
+	if (!strcmp(name, "-")) {
+		name = "@{-1}";
+		len = 5;
+	}
+
 	ret = get_sha1_basic(name, len, sha1, lookup_flags);
 	if (!ret)
 		return 0;
diff --git a/t/t4214-log-shorthand.sh b/t/t4214-log-shorthand.sh
new file mode 100755
index 0000000..dec966c
--- /dev/null
+++ b/t/t4214-log-shorthand.sh
@@ -0,0 +1,73 @@
+#!/bin/sh
+
+test_description='log can show previous branch using shorthand - for @{-1}'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo hello >world &&
+	git add world &&
+	git commit -m initial &&
+	echo "hello second time" >>world &&
+	git add world &&
+	git commit -m second &&
+	echo "hello other file" >>planet &&
+	git add planet &&
+	git commit -m third &&
+	echo "hello yet another file" >>city &&
+	git add city &&
+	git commit -m fourth
+'
+
+test_expect_success '"log -" should not work initially' '
+	test_must_fail git log -
+'
+
+test_expect_success '"log -" should work' '
+	git checkout -b testing-1 master^ &&
+	git checkout -b testing-2 master~2 &&
+	git checkout master &&
+
+	git log testing-2 >expect &&
+	git log - >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'symmetric revision range should work when one end is left empty' '
+	git checkout testing-2 &&
+	git checkout master &&
+	git log ...@{-1} > expect.first_empty &&
+	git log @{-1}... > expect.last_empty &&
+	git log ...- > actual.first_empty &&
+	git log -... > actual.last_empty &&
+	test_cmp expect.first_empty actual.first_empty &&
+	test_cmp expect.last_empty actual.last_empty
+'
+
+test_expect_success 'asymmetric revision range should work when one end is left empty' '
+	git checkout testing-2 &&
+	git checkout master &&
+	git log ..@{-1} > expect.first_empty &&
+	git log @{-1}.. > expect.last_empty &&
+	git log ..- > actual.first_empty &&
+	git log -.. > actual.last_empty &&
+	test_cmp expect.first_empty actual.first_empty &&
+	test_cmp expect.last_empty actual.last_empty
+'
+
+test_expect_success 'symmetric revision range should work when both ends are given' '
+	git checkout testing-2 &&
+	git checkout master &&
+	git log -...testing-1 >expect &&
+	git log testing-2...testing-1 >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'asymmetric revision range should work when both ends are given' '
+	git checkout testing-2 &&
+	git checkout master &&
+	git log -..testing-1 >expect &&
+	git log testing-2..testing-1 >actual &&
+	test_cmp expect actual
+'
+test_done
-- 
2.1.4