filter-branch fix and tests

Hi,

this is resend of the patch I sent two weeks ago. I've extended the commit
message to address Johannes' question and in the second patch I've added tests
for the fix.

Michal

The test 'rewrite submodule with another content' passes only with the
previous patch.

Signed-off-by: Michal Sojka <redacted>
---
 t/t7003-filter-branch.sh |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 9503875..39d4153 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh

@@ -306,4 +306,30 @@ test_expect_success '--remap-to-ancestor with filename filters' '
 	test $orig_invariant = $(git rev-parse invariant)
 '
 
+test_expect_success 'setup submodule' '
+	rm -rf * .*
+	git init &&
+	test_commit file &&
+	mkdir submod &&
+	submodurl="$PWD/submod"
+	( cd submod &&
+	  git init &&
+	  test_commit file-in-submod ) &&
+	git submodule add "$submodurl"
+	git commit -m "added submodule" &&
+	test_commit add-file &&
+	( cd submod && test_commit add-in-submodule ) &&
+	git add submod &&
+	git commit -m "changed submodule"
+'
+
+test_expect_success 'rewrite submodule with another content' '
+	git filter-branch --tree-filter "test -d submod && {
+					 rm -rf submod &&
+					 git rm -rf --quiet submod &&
+					 mkdir submod &&
+					 : > submod/file
+					 } || :"
+'
+
 test_done

-- 
1.6.6

When git filter-branch is used to replace a submodule with another
content, it always fails on the first commit. Consider a repository with
submod directory containing a submodule. If I want to remove the
submodule and replace it with a file, the following command fails.

git filter-branch --tree-filter 'rm -rf submod &&
				 git rm -q submod &&
				 mkdir submod &&
				 touch submod/file'

The error message is:
error: submod: is a directory - add files inside instead

The reason is that git diff-index, which generates the first part of the
list of files updated by the tree filter, emits also the removed
submodule even if it was replaced by a real directory.

Adding --ignored-submodules solves the problem for me and
tests in t7003-filter-branch.sh pass correctly.

If somebody wants to replace one revision of the module with another, it
can be done with --index-filter. Using --tree-filter for this has no
sense since --tree-filter "git submodule update --init" fails with
  Clone of '/tmp/submod' into submodule path 'submod' failed
so that the revision must be replaced only in index.

Signed-off-by: Michal Sojka <redacted>
---
 git-filter-branch.sh |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 195b5ef..d4ac7fb 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh

@@ -331,7 +331,7 @@ while read commit parents; do
 			die "tree filter failed: $filter_tree"
 
 		(
-			git diff-index -r --name-only $commit &&
+			git diff-index -r --name-only --ignore-submodules $commit && 
 			git ls-files --others
 		) > "$tempdir"/tree-state || exit
 		git update-index --add --replace --remove --stdin \

-- 
1.6.6