[PATCH 2/3] fast-import: treat filemodify with empty tree as delete

[Jonathan Nieder <jrnieder@gmail.com>]

Date: Sat, 11 Dec 2010 16:42:28 -0600

Traditionally, git trees do not contain entries for empty
subdirectories.  Generally speaking, subtrees are not created or
destroyed explicitly; instead, they automatically appear when needed
to hold regular files, symlinks, and submodules.

v1.7.3-rc0~75^2 (Teach fast-import to import subtrees named by tree
id, 2010-06-30) changed that, by allowing an empty subtree to be
included in a fast-import stream explicitly:

	M 040000 4b825dc642cb6eb9a060e54bf8d69288fbee4904 subdir

That was unintentional.  Better and more closely analogous to "git
read-tree --prefix" to treat such an input line as a request to delete
("to empty") subdir.

Noticed-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
If this seems like a good idea it might be a candidate for v1.7.4.x.
Perhaps fsck.c should learn a "no empty trees" rule, too.

 fast-import.c          |   10 ++++++++
 t/t9300-fast-import.sh |   58 +++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index a5cea45..385d12d 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -2231,6 +2231,16 @@ static void file_change_m(struct branch *b)
 		p = uq.buf;
 	}
 
+	/*
+	 * Git does not track empty, non-toplevel directories.
+	 */
+	if (S_ISDIR(mode) &&
+	    !memcmp(sha1, (const unsigned char *) EMPTY_TREE_SHA1_BIN, 20) &&
+	    *p) {
+		tree_content_remove(&b->branch_tree, p, NULL);
+		return;
+	}
+
 	if (S_ISGITLINK(mode)) {
 		if (inline_data)
 			die("Git links cannot be specified 'inline': %s",
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 53aad51..b9aa3f0 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -42,6 +42,14 @@ echo "$@"'
 
 >empty
 
+test_expect_success 'setup: have pipes?' '
+	rm -f frob &&
+	if mkfifo frob
+	then
+		test_set_prereq PIPE
+	fi
+'
+
 ###
 ### series A
 ###
@@ -899,6 +907,48 @@ test_expect_success \
 	 compare_diff_raw expect actual'
 
 test_expect_success \
+	'N: delete directory by copying' \
+	'cat >expect <<-\EOF &&
+	OBJID
+	:100644 000000 OBJID OBJID D	foo/bar/qux
+	OBJID
+	:000000 100644 OBJID OBJID A	foo/bar/baz
+	:000000 100644 OBJID OBJID A	foo/bar/qux
+	EOF
+	 empty_tree=$(git mktree </dev/null) &&
+	 cat >input <<-INPUT_END &&
+	commit refs/heads/N-delete
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	collect data to be deleted
+	COMMIT
+
+	deleteall
+	M 100644 inline foo/bar/baz
+	data <<DATA_END
+	hello
+	DATA_END
+	C "foo/bar/baz" "foo/bar/qux"
+	C "foo/bar/baz" "foo/bar/quux/1"
+	C "foo/bar/baz" "foo/bar/quuux"
+	M 040000 $empty_tree foo/bar/quux
+	M 040000 $empty_tree foo/bar/quuux
+
+	commit refs/heads/N-delete
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	delete subdirectory
+	COMMIT
+
+	M 040000 $empty_tree foo/bar/qux
+	INPUT_END
+	 git fast-import <input &&
+	 git rev-list N-delete |
+		git diff-tree -r --stdin --root --always |
+		sed -e "s/$_x40/OBJID/g" >actual &&
+	 test_cmp expect actual'
+
+test_expect_success \
 	'N: copy root directory by tree hash' \
 	'cat >expect <<-\EOF &&
 	:100755 000000 f1fb5da718392694d0076d677d6d0e364c79b0bc 0000000000000000000000000000000000000000 D	file3/newf
@@ -1898,14 +1948,6 @@ test_expect_success 'R: print two blobs to stdout' '
 	test_cmp expect actual
 '
 
-test_expect_success 'setup: have pipes?' '
-	rm -f frob &&
-	if mkfifo frob
-	then
-		test_set_prereq PIPE
-	fi
-'
-
 test_expect_success PIPE 'R: copy using cat-file' '
 	expect_id=$(git hash-object big) &&
 	expect_len=$(wc -c <big) &&
-- 
1.7.4.rc0.580.g89dc.dirty