filter-branch: Grok special characters in tag names

The tag rewriting code used a 'sed' expression to substitute the new tag
name into the corresponding field of the annotated tag object. But this is
problematic if the tag name contains special characters. In particular,
if the tag name contained a slash, then the 'sed' expression had a syntax
error. We now protect against this by using 'printf' to assemble the
tag header.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-filter-branch.sh

@@ -416,15 +416,17 @@ if [ "$filter_tag_name" ]; then
 		echo "$ref -> $new_ref ($sha1 -> $new_sha1)"
 
 		if [ "$type" = "tag" ]; then
-			new_sha1=$(git cat-file tag "$ref" |
+			new_sha1=$( ( printf 'object %s\ntype commit\ntag %s\n' \
+						"$new_sha1" "$new_ref"
+				git cat-file tag "$ref" |
 				sed -n \
 				    -e "1,/^$/{
-					  s/^object .*/object $new_sha1/
-					  s/^type .*/type commit/
-					  s/^tag .*/tag $new_ref/
+					  /^object /d
+					  /^type /d
+					  /^tag /d
 					}" \
 				    -e '/^-----BEGIN PGP SIGNATURE-----/q' \
-				    -e 'p' |
+				    -e 'p' ) |
 				git mktag) ||
 				die "Could not create new tag object for $ref"
 			if git cat-file tag "$ref" | \

t/t7003-filter-branch.sh

@@ -250,4 +250,12 @@ test_expect_success 'Tag name filtering strips gpg signature' '
 	test_cmp expect actual
 '
 
+test_expect_success 'Tag name filtering allows slashes in tag names' '
+	git tag -m tag-with-slash X/1 &&
+	git cat-file tag X/1 | sed -e s,X/1,X/2, > expect &&
+	git filter-branch -f --tag-name-filter "echo X/2" &&
+	git cat-file tag X/2 > actual &&
+	test_cmp expect actual
+'
+
 test_done