[PATCH v2 1/2] [GSOC] cat-file: handle trivial --batch format with --batch-all-objects

["ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>]

From: ZheNing Hu <adlternative@gmail.com>

The --batch code to print an object assumes we found out the type of
the object from calling oid_object_info_extended(). This is true for
the default format, but even in a custom format, we manually modify
the object_info struct to ask for the type.

This assumption was broken by 845de33a5b (cat-file: avoid noop calls
to sha1_object_info_extended, 2016-05-18). That commit skips the call
to oid_object_info_extended() entirely when --batch-all-objects is in
use, and the custom format does not include any placeholders that
require calling it.

Or when the custom format only include placeholders like %(objectname) or
%(rest), oid_object_info_extended() will not get the type of the object.

This results in an error when we try to confirm that the type didn't
change:

$ git cat-file --batch=batman --batch-all-objects
batman
fatal: object 000023961a0c02d6e21dc51ea3484ff71abf1c74 changed type!?

and also has other subtle effects (e.g., we'd fail to stream a blob,
since we don't realize it's a blob in the first place).

We can fix this by flipping the order of the setup. The check for "do
we need to get the object info" must come _after_ we've decided
whether we need to look up the type.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 builtin/cat-file.c  | 13 +++++++------
 t/t1006-cat-file.sh | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 5ebf13359e83..02461bb5ea6f 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -512,12 +512,6 @@ static int batch_objects(struct batch_options *opt)
 	if (opt->cmdmode)
 		data.split_on_whitespace = 1;
 
-	if (opt->all_objects) {
-		struct object_info empty = OBJECT_INFO_INIT;
-		if (!memcmp(&data.info, &empty, sizeof(empty)))
-			data.skip_object_info = 1;
-	}
-
 	/*
 	 * If we are printing out the object, then always fill in the type,
 	 * since we will want to decide whether or not to stream.
@@ -525,6 +519,13 @@ static int batch_objects(struct batch_options *opt)
 	if (opt->print_contents)
 		data.info.typep = &data.type;
 
+	if (opt->all_objects) {
+		struct object_info empty = OBJECT_INFO_INIT;
+
+		if (!memcmp(&data.info, &empty, sizeof(empty)))
+			data.skip_object_info = 1;
+	}
+
 	if (opt->all_objects) {
 		struct object_cb_data cb;
 
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 5d2dc99b74ad..18b3779ccb60 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -586,4 +586,26 @@ test_expect_success 'cat-file --unordered works' '
 	test_cmp expect actual
 '
 
+test_expect_success 'set up object list for --batch-all-objects tests' '
+	git -C all-two cat-file --batch-all-objects --batch-check="%(objectname)" >objects
+'
+
+test_expect_success 'cat-file --batch="%(objectname)" with --batch-all-objects will work' '
+	git -C all-two cat-file --batch="%(objectname)" <objects >expect &&
+	git -C all-two cat-file --batch-all-objects --batch="%(objectname)" >actual &&
+	cmp expect actual
+'
+
+test_expect_success 'cat-file --batch="%(rest)" with --batch-all-objects will work' '
+	git -C all-two cat-file --batch="%(rest)" <objects >expect &&
+	git -C all-two cat-file --batch-all-objects --batch="%(rest)" >actual &&
+	cmp expect actual
+'
+
+test_expect_success 'cat-file --batch="batman" with --batch-all-objects will work' '
+	git -C all-two cat-file --batch="batman" <objects >expect &&
+	git -C all-two cat-file --batch-all-objects --batch="batman" >actual &&
+	cmp expect actual
+'
+
 test_done
-- 
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