[RFC PATCH 3/5] t4211-line-log: add tests for parent oids

["SZEDER Gábor" <szeder.dev@gmail.com>]

None of the tests in 't4211-line-log.sh' really check which parent
object IDs are shown in the output, either implicitly as part of
"Merge: ..." lines [1] or explicitly via the '%p' or '%P' format
specifiers in a custom pretty format.

Add two tests to 't4211-line-log.sh' to check which parent object IDs
are shown, one without and one with explicitly requested parent
rewriting, IOW without and with the '--parents' option.

The test without '--parents' is marked as failing, because without
that option parent rewriting should not be performed, and thus the
parent object ID should be that of the immediate parent, just like in
case of a pathspec-limited history traversal without parent rewriting.
The current line-level log implementation, however, performs parent
rewriting unconditionally and without a possibility to turn it off,
and, consequently, it shows the object ID of the most recent ancestor
that modified the given line range.

In both of these new tests we only really care about the object IDs of
the listed commits and their parents, but not the diffs of the line
ranges; the diffs have already been thoroughly checked in the previous
tests.

[1] While one of the tests ('-M -L ':f:b.c' parallel-change') does
    list a merge commit, both of its parents happen to modify the
    given line range and are listed as well, so the implications of
    parent rewriting remained hidden and untested.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 t/t4211-line-log.sh | 68 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 1db7bd0f59..c378a453de 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -132,4 +132,72 @@ test_expect_success '--raw is forbidden' '
 	test_must_fail git log -L1,24:b.c --raw
 '
 
+# Create the following linear history, where each commit does what its
+# subject line promises:
+#
+#   * 66c6410 Modify func2() in file.c
+#   * 50834e5 Modify other-file
+#   * fe5851c Modify func1() in file.c
+#   * 8c7c7dd Add other-file
+#   * d5f4417 Add func1() and func2() in file.c
+test_expect_success 'setup for checking line-log and parent oids' '
+	git checkout --orphan parent-oids &&
+	git reset --hard &&
+
+	cat >file.c <<-\EOF &&
+	int func1()
+	{
+	    return F1;
+	}
+
+	int func2()
+	{
+	    return F2;
+	}
+	EOF
+	git add file.c &&
+	test_tick &&
+	git commit -m "Add func1() and func2() in file.c" &&
+
+	echo 1 >other-file &&
+	git add other-file &&
+	git commit -m "Add other-file" &&
+
+	sed -e "s/F1/F1 + 1/" file.c >tmp &&
+	mv tmp file.c &&
+	git commit -a -m "Modify func1() in file.c" &&
+
+	echo 2 >other-file &&
+	git commit -a -m "Modify other-file" &&
+
+	sed -e "s/F2/F2 + 2/" file.c >tmp &&
+	mv tmp file.c &&
+	git commit -a -m "Modify func2() in file.c" &&
+
+	head_oid=$(git rev-parse --short HEAD) &&
+	prev_oid=$(git rev-parse --short HEAD^) &&
+	root_oid=$(git rev-parse --short HEAD~4)
+'
+
+# Parent oid should be from immediate parent.
+test_expect_failure 'parent oids without parent rewriting' '
+	cat >expect <<-EOF &&
+	$head_oid $prev_oid Modify func2() in file.c
+	$root_oid  Add func1() and func2() in file.c
+	EOF
+	git log --format="%h %p %s" --no-patch -L:func2:file.c >actual &&
+	test_cmp expect actual
+'
+
+# Parent oid should be from the most recent ancestor touching func2(),
+# i.e. in this case from the root commit.
+test_expect_success 'parent oids with parent rewriting' '
+	cat >expect <<-EOF &&
+	$head_oid $root_oid Modify func2() in file.c
+	$root_oid  Add func1() and func2() in file.c
+	EOF
+	git log --format="%h %p %s" --no-patch -L:func2:file.c --parents >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.23.0.349.g73f10e387d