[PATCH v4] filter-branch: fix errors caused by refs that point at non-committish

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

"git filter-branch -- --all" prints error messages when processing refs that
point at objects that are not committish. Such refs can be created by
"git replace" with trees or blobs. And also "git tag" with trees or blobs can
create such refs.

Filter these problematic refs out early, before they are seen by the logic to
see which refs have been modified and which have been left intact (which is
where the unwanted error messages come from), and warn that these refs are left
unwritten while doing so.

Signed-off-by: Yuki Kokubun <orga.chem.job@gmail.com>
---
 git-filter-branch.sh     | 14 ++++++++++++--
 t/t7003-filter-branch.sh | 14 ++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 1b7e4b2cd..41efecb28 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -251,8 +251,18 @@ done < "$tempdir"/backup-refs
 
 # The refs should be updated if their heads were rewritten
 git rev-parse --no-flags --revs-only --symbolic-full-name \
-	--default HEAD "$@" > "$tempdir"/raw-heads || exit
-sed -e '/^^/d' "$tempdir"/raw-heads >"$tempdir"/heads
+	--default HEAD "$@" > "$tempdir"/raw-refs || exit
+while read ref
+do
+	case "$ref" in ^?*) continue ;; esac
+
+	if git rev-parse --verify "$ref"^0 >/dev/null 2>&1
+	then
+		echo "$ref"
+	else
+		warn "WARNING: not rewriting '$ref' (not a committish)"
+	fi
+done >"$tempdir"/heads <"$tempdir"/raw-refs
 
 test -s "$tempdir"/heads ||
 	die "You must specify a ref to rewrite."
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 7cb60799b..04f79f32b 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -470,4 +470,18 @@ test_expect_success 'tree-filter deals with object name vs pathname ambiguity' '
 	git show HEAD:$ambiguous
 '
 
+test_expect_success 'rewrite repository including refs that point at 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 tag -a -m "tag to a tree" treetag $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