[PATCH v4 1/2] 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 | 25 +++++++++++++++++++++++--
 tree-walk.c            | 12 +++++++-----
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/t/t1007-hash-object.sh b/t/t1007-hash-object.sh
index acca9ac..c5245c5 100755
--- a/t/t1007-hash-object.sh
+++ b/t/t1007-hash-object.sh
@@ -183,9 +183,30 @@ 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 &&
+	test_i18ngrep "too-short tree object" err
+'
+
+hex2oct() {
+    perl -ne 'printf "\\%03o", hex for /../g'
+}
+
+test_expect_success 'malformed mode in tree' '
+	hex_sha1=$(echo foo | git hash-object --stdin -w) &&
+	bin_sha1=$(echo $hex_sha1 | hex2oct) &&
+	printf "9100644 \0$bin_sha1" >tree-with-malformed-mode &&
+	test_must_fail git hash-object -t tree tree-with-malformed-mode 2>err &&
+	test_i18ngrep "malformed mode in tree entry" err
+'
+
+test_expect_success 'empty filename in tree' '
+	hex_sha1=$(echo foo | git hash-object --stdin -w) &&
+	bin_sha1=$(echo $hex_sha1 | hex2oct) &&
+	printf "100644 \0$bin_sha1" >tree-with-empty-filename &&
+	test_must_fail git hash-object -t tree tree-with-empty-filename 2>err &&
+	test_i18ngrep "empty filename in tree entry" err
 '
 
 test_expect_success 'corrupt commit' '
diff --git a/tree-walk.c b/tree-walk.c
index ce27842..24f9a0f 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