reset: add a few tests for "git reset --merge"

Commit 9e8ecea ("Add 'merge' mode to 'git reset'", 2008-12-01),
added the --merge option to git reset, but there were no test cases
for it.

This was not a big problem because "git reset" was just forking and
execing "git read-tree", but this will change in a following patch.

So let's add a few test cases to make sure that there will be no
regression.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7110-reset-merge.sh

@@ -0,0 +1,159 @@
+#!/bin/sh
+#
+# Copyright (c) 2009 Christian Couder
+#
+
+test_description='Tests for "git reset --merge"'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+    for i in 1 2 3; do echo line $i; done >file1 &&
+    cat file1 >file2 &&
+    git add file1 file2 &&
+    test_tick &&
+    git commit -m "Initial commit" &&
+    git tag initial &&
+    echo line 4 >>file1 &&
+    cat file1 >file2 &&
+    test_tick &&
+    git commit -m "add line 4 to file1" file1 &&
+    git tag second
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     C       C     C    D     --merge  D       D     D
+# file2:     C       D     D    D     --merge  C       D     D
+test_expect_success 'reset --merge is ok with changes in file it does not touch' '
+    git reset --merge HEAD^ &&
+    ! grep 4 file1 &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse initial)" &&
+    test -z "$(git diff --cached)"
+'
+
+test_expect_success 'reset --merge is ok when switching back' '
+    git reset --merge second &&
+    grep 4 file1 &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse second)" &&
+    test -z "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     B       B     C    D     --merge  D       D     D
+# file2:     C       D     D    D     --merge  C       D     D
+test_expect_success 'reset --merge discards changes added to index (1)' '
+    git reset --hard second &&
+    cat file1 >file2 &&
+    echo "line 5" >> file1 &&
+    git add file1 &&
+    git reset --merge HEAD^ &&
+    ! grep 4 file1 &&
+    ! grep 5 file1 &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse initial)" &&
+    test -z "$(git diff --cached)"
+'
+
+test_expect_success 'reset --merge is ok again when switching back (1)' '
+    git reset --hard initial &&
+    echo "line 5" >> file2 &&
+    git add file2 &&
+    git reset --merge second &&
+    ! grep 4 file2 &&
+    ! grep 5 file1 &&
+    grep 4 file1 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse second)" &&
+    test -z "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     C       C     C    D     --merge  D       D     D
+# file2:     C       C     D    D     --merge  D       D     D
+test_expect_success 'reset --merge discards changes added to index (2)' '
+    git reset --hard second &&
+    echo "line 4" >> file2 &&
+    git add file2 &&
+    git reset --merge HEAD^ &&
+    ! grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse initial)" &&
+    test -z "$(git diff)" &&
+    test -z "$(git diff --cached)"
+'
+
+test_expect_success 'reset --merge is ok again when switching back (2)' '
+    git reset --hard initial &&
+    git reset --merge second &&
+    ! grep 4 file2 &&
+    grep 4 file1 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse second)" &&
+    test -z "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     A       B     B    C     --merge  (disallowed)
+test_expect_success 'reset --merge fails with changes in file it touches' '
+    git reset --hard second &&
+    echo "line 5" >> file1 &&
+    test_tick &&
+    git commit -m "add line 5" file1 &&
+    sed -e "s/line 1/changed line 1/" <file1 >file3 &&
+    mv file3 file1 &&
+    test_must_fail git reset --merge HEAD^ 2>err.log &&
+    grep file1 err.log | grep "not uptodate"
+'
+
+test_expect_success 'setup 2 different branches' '
+    git reset --hard second &&
+    git branch branch1 &&
+    git branch branch2 &&
+    git checkout branch1 &&
+    echo "line 5 in branch1" >> file1 &&
+    test_tick &&
+    git commit -a -m "change in branch1" &&
+    git checkout branch2 &&
+    echo "line 5 in branch2" >> file1 &&
+    test_tick &&
+    git commit -a -m "change in branch2" &&
+    git tag third
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     X       U     B    C     --merge  (disallowed)
+test_expect_success '"reset --merge HEAD^" fails with pending merge' '
+    test_must_fail git merge branch1 &&
+    test_must_fail git reset --merge HEAD^ &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse third)" &&
+    test -n "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     X       U     B    B     --merge  (disallowed)
+test_expect_success '"reset --merge HEAD" fails with pending merge' '
+    git reset --hard third &&
+    test_must_fail git merge branch1 &&
+    test_must_fail git reset --merge HEAD &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse third)" &&
+    test -n "$(git diff --cached)"
+'
+
+test_done