[PATCH] t4202 (log): add failing test for log with subtree

When using 'git subtree' to add an external project at a given prefix,
log of a pathspec within the prefix fails to give the expected output.
This failure can be interpreted as log expecting all trees to be read
into /.  Document this bug by adding a failing test.

Signed-off-by: Ramkumar Ramachandra <redacted>
---
 I normally don't use git-subtree, but happened to notice this when I
 was checking it out: a 'git log <pathspec>', when referring to a file
 inside the subtree, doesn't work as expected: it only displays the
 HEAD commit.  I know this is not related to git-subtree at all, and
 has to do with how 'git log' (and probably 'git merge -Xsubtree',
 'git merge -s subtree') works.  I suspect that 'git log' expects all
 trees to be read into /, and I've tried to prove this with a failing
 test.

 I think this is a bug, but I might be missing something.  Can someone
 tell me what is actually happening?

 t/t4202-log.sh | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 9243a97..523c1be 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh

@@ -168,6 +168,37 @@ test_expect_success 'git log --follow' '
 
 '
 
+test_expect_failure 'log pathspec in tree read into prefix' '
+	git checkout --orphan subtree &&
+	git rm -rf . &&
+	echo foodle >ichi &&
+	git add ichi &&
+	test_tick &&
+	git commit -m foom &&
+	echo moodle >unrelated &&
+	git add unrelated &&
+	test_tick &&
+	git commit -m quux &&
+	subtree_h=$(git rev-parse HEAD) &&
+	git checkout master &&
+	orig_h=$(git rev-parse HEAD) &&
+	git read-tree --prefix=bar $subtree_h &&
+	new_t=$(git write-tree) &&
+	new_h=$(echo "new subtree" |
+	git commit-tree $new_t -p $orig_h -p $subtree_h) &&
+	git reset --hard $new_h &&
+	(
+		cd bar &&
+		git log --oneline ichi >../actual
+	) &&
+	cat >expect <<-\EOF &&
+	61dcd8e new subtree
+	130a8fb foom
+	EOF
+	git reset --hard HEAD~1 &&
+	test_cmp expect actual
+'
+
 cat > expect << EOF
 804a787 sixth
 394ef78 fifth

-- 
1.8.2.1.546.gea3475a