[PATCH 1/3] tree-walk: be more specific about corrupt tree errors

[David Turner <dturner@twosigma.com>]

From: Jeff King <peff@peff.net>

When the tree-walker runs into an error, it just calls
die(), and the message is always "corrupt tree file".
However, we are actually covering several cases here; let's
give the user a hint about what happened.

Let's also avoid using the word "corrupt", which makes it
seem like the data bit-rotted on disk. Our sha1 check would
already have found that. These errors are ones of data that
is malformed in the first place.

Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: Jeff King <peff@peff.net>
---
 t/t1007-hash-object.sh           |  15 +++++++++++++--
 t/t1007/.gitattributes           |   1 +
 t/t1007/tree-with-empty-filename | Bin 0 -> 28 bytes
 t/t1007/tree-with-malformed-mode | Bin 0 -> 39 bytes
 tree-walk.c                      |  12 +++++++-----
 5 files changed, 21 insertions(+), 7 deletions(-)
 create mode 100644 t/t1007/.gitattributes
 create mode 100644 t/t1007/tree-with-empty-filename
 create mode 100644 t/t1007/tree-with-malformed-mode

diff --git a/t/t1007-hash-object.sh b/t/t1007-hash-object.sh
index acca9ac..f21848b 100755
--- a/t/t1007-hash-object.sh
+++ b/t/t1007-hash-object.sh
@@ -183,9 +183,20 @@ for args in "-w --stdin-paths" "--stdin-paths -w"; do
 	pop_repo
 done
 
-test_expect_success 'corrupt tree' '
+test_expect_success 'too-short tree' '
 	echo abc >malformed-tree &&
-	test_must_fail git hash-object -t tree malformed-tree
+	test_must_fail git hash-object -t tree malformed-tree 2>err &&
+	grep "too-short tree object" err
+'
+
+test_expect_success 'malformed mode in tree' '
+	test_must_fail git hash-object -t tree ../t1007/tree-with-malformed-mode 2>err &&
+	grep "malformed mode in tree entry" err
+'
+
+test_expect_success 'empty filename in tree' '
+	test_must_fail git hash-object -t tree ../t1007/tree-with-empty-filename 2>err &&
+	grep "empty filename in tree entry" err
 '
 
 test_expect_success 'corrupt commit' '
diff --git a/t/t1007/.gitattributes b/t/t1007/.gitattributes
new file mode 100644
index 0000000..7352ef5
--- /dev/null
+++ b/t/t1007/.gitattributes
@@ -0,0 +1 @@
+tree-with-*	-diff
diff --git a/t/t1007/tree-with-empty-filename b/t/t1007/tree-with-empty-filename
new file mode 100644
index 0000000000000000000000000000000000000000..aeb1ceb20e485eebd0acbb81c974d1c6fedcc1fe
GIT binary patch
literal 28
kcmXpsFfcPQQDAsB_tET47q2;ccWbUIkGgT_Nl)-Z0Hx{;SO5S3

literal 0
HcmV?d00001

diff --git a/t/t1007/tree-with-malformed-mode b/t/t1007/tree-with-malformed-mode
new file mode 100644
index 0000000000000000000000000000000000000000..24aa84d60ef8e269fb0b29c67b5208639b9da3ae
GIT binary patch
literal 39
vcmYewPcJRb%}+^HNXyJg%}dNpWq3CC(d<nZuQ_{nYpyGgx^d`9Pw+$lU*Quk

literal 0
HcmV?d00001

diff --git a/tree-walk.c b/tree-walk.c
index ce27842..ba544cf 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -27,12 +27,14 @@ static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned
 	const char *path;
 	unsigned int mode, len;
 
-	if (size < 24 || buf[size - 21])
-		die("corrupt tree file");
+	if (size < 23 || buf[size - 21])
+		die("too-short tree object");
 
 	path = get_mode(buf, &mode);
-	if (!path || !*path)
-		die("corrupt tree file");
+	if (!path)
+		die("malformed mode in tree entry for tree");
+	if (!*path)
+		die("empty filename in tree entry for tree");
 	len = strlen(path) + 1;
 
 	/* Initialize the descriptor entry */
@@ -81,7 +83,7 @@ void update_tree_entry(struct tree_desc *desc)
 	unsigned long len = end - (const unsigned char *)buf;
 
 	if (size < len)
-		die("corrupt tree file");
+		die("too-short tree file");
 	buf = end;
 	size -= len;
 	desc->buffer = buf;
-- 
2.8.0.rc4.22.g8ae061a