[PATCH] fast-export: deletion action first

[Miguel Torroja <miguel.torroja@gmail.com>]

The delete operations of the fast-export output should precede any addition
belonging to the same commit, Addition and deletion with the same name
entry could happen in case of file to directory and viceversa.

As an equal comparison doesn't have any deterministic final order,
it's better to keep original diff order input when there is no prefer order
( that's done comparing pointers)

The fast-export sorting was added in 060df62 (fast-export: Fix output
order of D/F changes). That change was made in order to fix the case of
directory to file in the same commit, but it broke the reverse case
(File to directory).

The test "file becomes directory" has been added in order to exercise
the original motivation of the deletion reorder.

Signed-off-by: Miguel Torroja <miguel.torroja@gmail.com>
---
 builtin/fast-export.c  | 32 +++++++++++++++-----------------
 t/t9350-fast-export.sh | 25 +++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index e022063..e82f654 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -260,26 +260,19 @@ static void export_blob(const struct object_id *oid)
 		free(buf);
 }
 
-static int depth_first(const void *a_, const void *b_)
+/*
+ * Compares two diff types to order based on output priorities.
+ */
+static int diff_type_cmp(const void *a_, const void *b_)
 {
 	const struct diff_filepair *a = *((const struct diff_filepair **)a_);
 	const struct diff_filepair *b = *((const struct diff_filepair **)b_);
-	const char *name_a, *name_b;
-	int len_a, len_b, len;
 	int cmp;
 
-	name_a = a->one ? a->one->path : a->two->path;
-	name_b = b->one ? b->one->path : b->two->path;
-
-	len_a = strlen(name_a);
-	len_b = strlen(name_b);
-	len = (len_a < len_b) ? len_a : len_b;
-
-	/* strcmp will sort 'd' before 'd/e', we want 'd/e' before 'd' */
-	cmp = memcmp(name_a, name_b, len);
-	if (cmp)
-		return cmp;
-	cmp = len_b - len_a;
+	/*
+	 * Move Delete entries first so that an addition is always reported after
+	 */
+	cmp = (b->status == DIFF_STATUS_DELETED) - (a->status == DIFF_STATUS_DELETED);
 	if (cmp)
 		return cmp;
 	/*
@@ -287,7 +280,12 @@ static int depth_first(const void *a_, const void *b_)
 	 * appear in the output before it is renamed (e.g., when a file
 	 * was copied and renamed in the same commit).
 	 */
-	return (a->status == 'R') - (b->status == 'R');
+	cmp = (a->status == DIFF_STATUS_RENAMED) - (b->status == DIFF_STATUS_RENAMED);
+	if (cmp)
+		return cmp;
+
+	/* For the remaining cases we keep the original ordering comparing the pointers */
+	return (a-b);
 }
 
 static void print_path_1(const char *path)
@@ -347,7 +345,7 @@ static void show_filemodify(struct diff_queue_struct *q,
 	 * Handle files below a directory first, in case they are all deleted
 	 * and the directory changes to a file or symlink.
 	 */
-	QSORT(q->queue, q->nr, depth_first);
+	QSORT(q->queue, q->nr, diff_type_cmp);
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filespec *ospec = q->queue[i]->one;
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index b5149fd..d4f369a 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -419,6 +419,31 @@ test_expect_success 'directory becomes symlink'        '
 	(cd result && git show master:foo)
 '
 
+test_expect_success 'file becomes directory'  '
+	git init filetodir_orig &&
+	git init --bare filetodir_replica.git &&
+	(
+		cd filetodir_orig &&
+		echo foo > filethendir &&
+		git add filethendir &&
+		test_tick &&
+		git commit -mfile &&
+		git rm filethendir &&
+		mkdir filethendir &&
+		echo bar > filethendir/a &&
+		git add filethendir/a &&
+		test_tick &&
+		git commit -mdir
+	) &&
+	git --git-dir=filetodir_orig/.git fast-export master  |
+		git --git-dir=filetodir_replica.git/ fast-import &&
+	(
+		ORIG=$(git --git-dir=filetodir_orig/.git rev-parse --verify master) &&
+		REPLICA=$(git --git-dir=filetodir_replica.git rev-parse --verify master) &&
+		test $ORIG = $REPLICA
+	)
+'
+
 test_expect_success 'fast-export quotes pathnames' '
 	git init crazy-paths &&
 	(cd crazy-paths &&
-- 
2.1.4