[PATCH] filter-branch: consider refs/replace can refer to an object other than commit

[Yuki Kokubun <orga.chem.job@gmail.com>]

"git filter-branch -- --all" can be confused when refs that refer to objects
other than commits exists.
Because "git rev-parse --all" that is internally used can return refs that
refer to an object other than commit. But it is not considered in the phase of
updating refs. Such refs can be created by "git replace" with objects other than
commits.

Signed-off-by: Yuki Kokubun <orga.chem.job@gmail.com>
---
 git-filter-branch.sh     |  3 +++
 t/t7003-filter-branch.sh | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 1b7e4b2cd..a9fafe64f 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -479,6 +479,9 @@ do
 	# avoid rewriting a ref twice
 	test -f "$orig_namespace$ref" && continue
 
+	# refs/replace can point to a non commit object
+	test $(git cat-file -t "$ref") = commit || continue
+
 	sha1=$(git rev-parse "$ref"^0)
 	rewritten=$(map $sha1)
 
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 7cb60799b..efeaf5887 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -470,4 +470,17 @@ test_expect_success 'tree-filter deals with object name vs pathname ambiguity' '
 	git show HEAD:$ambiguous
 '
 
+test_expect_success 'rewrite repository including refs/replace that point to non commit object' '
+	test_when_finished "git reset --hard original" &&
+	tree=$(git rev-parse HEAD^{tree}) &&
+	test_when_finished "git replace -d $tree" &&
+	echo A >new &&
+	git add new &&
+	new_tree=$(git write-tree) &&
+	git replace $tree $new_tree &&
+	git reset --hard HEAD &&
+	git filter-branch -f -- --all >filter-output 2>&1 &&
+	! fgrep fatal filter-output
+'
+
 test_done
-- 
2.16.2.18.g09cb46d