threads / patch / 63566

patch, 3 partscat-file: add %(objectmode) and submodule message to batch commands

Subject: [PATCH 0/3] cat-file: add %(objectmode) and submodule message to batch commands

## tl;dr

10 messages between Jun 2, 2025 and Jun 5, 2025. Diffs are folded; open one to read it.

replies: 9people: 3as markdown or json

Victoria Dye via GitGitGadget· Jun 2, 2025, 18:55 UTC · lore

This series re-attempts the changes proposed last year [1] for extending the information about tree entries available from the 'cat-file' batch format commands. It also (hopefully) addresses the initial round of feedback that series received.

The first patch updates 't1006-cat-file.sh' to test non-OID object specifications. In response to the feedback in [2], I added more careful quoting and a couple tests using paths with spaces. This change revealed a (likely known) limitation of the '%(rest)' atom when processing object names with spaces. To make that limitation explicit, I marked the relevant test as expected to fail.

The second patch adds "mode" support. This is essentially unchanged from its initial submission, save for some conflict resolution in the test script.

The final patch takes a different approach to submodule resolution than the initial submission; rather than treat the entry as a "regular" commit object with empty content, we now print an error message similar to the "missing", "ambiguous", etc. cases, but with the tree entry's OID rather than the input object name.

As for the motivation behind the change (re: [3]), the goal of this series is to be able to get more of the information available internally about an object in 'cat-file --batch[*]' -- in the case of a tree entry, the main things missing were the file mode and the presence (and OID) of submodule pointers. As Junio mentioned in [4], using a single long-running process to resolve objects is far more performant than spawning multiple processes to resolve tree entries with something like 'ls-tree', especially when resolving entries across multiple trees or resolving a mix of tree entries and OIDs, refnames, etc. The object resolution logic in 'cat-file' meant that the mode & submodule OID information were already (mostly) available, but we didn't have a way to output it.

The intent of this series is to make the new format options/outputs to get those fields as unobtrusive as possible, but I'm happy to do something more like the previous series if that would be preferable.

[1] https://lore.kernel.org/git/pull.1689.git.1710183362.gitgitgadget@gmail.com/ [2] https://lore.kernel.org/git/xmqqle6oo2ns.fsf@gitster.g/ [3] https://lore.kernel.org/git/20240312221758.GA109417@coredump.intra.peff.net/ [4] https://lore.kernel.org/git/xmqq1q8fl05r.fsf@gitster.g/

Victoria Dye (3):
  t1006: update 'run_tests' to test generic object specifiers
  cat-file: add %(objectmode) atom
  cat-file.c: add batch handling for submodules
 Documentation/git-cat-file.adoc |  13 ++++
 builtin/cat-file.c              |  14 +++-
 t/t1006-cat-file.sh             | 111 +++++++++++++++++++++++---------
 3 files changed, 103 insertions(+), 35 deletions(-)
base-commit: 7014b55638da979331baf8dc31c4e1d697cf2d67
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1929%2Fvdye%2Fvdye%2Fcat-file-mode-submodule-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1929/vdye/vdye/cat-file-mode-submodule-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1929
-- 
gitgitgadget
Victoria Dye via GitGitGadget· Jun 2, 2025, 18:55 UTC · re: Victoria Dye via GitGitGadget · lore

[PATCH 1/3] t1006: update 'run_tests' to test generic object specifiers

From: Victoria Dye <vdye@github.com>

Update the 'run_tests' test wrapper so that the first argument may refer to any specifier that uniquely identifies an object (e.g. a ref name, '<OID>:<path>', '<OID>^{<type>}', etc.), rather than only a full object ID.

Also add tests that use non-OID identifiers, ensuring appropriate parsing in 'cat-file'. The identifiers used in some of the added tests include a space, which is incompatible with the '%(rest)' atom. To accommodate that without removing the test case, use 'test_expect_failure' when 'object_name' includes a space.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Victoria Dye <vdye@github.com>
---
 t/t1006-cat-file.sh | 56 +++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 20 deletions(-)
Show changes to t/t1006-cat-file.sh +36 −20
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 317da6869c88..7c9512a6b439 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -113,53 +113,54 @@ strlen () {
 
 run_tests () {
     type=$1
-    oid=$2
+    object_name="$2"
     size=$3
     content=$4
     pretty_content=$5
+    oid=${6:-"$object_name"}
 
     batch_output="$oid $type $size
 $content"
 
     test_expect_success "$type exists" '
-	git cat-file -e $oid
+	git cat-file -e "$object_name"
     '
 
     test_expect_success "Type of $type is correct" '
 	echo $type >expect &&
-	git cat-file -t $oid >actual &&
+	git cat-file -t "$object_name" >actual &&
 	test_cmp expect actual
     '
 
     test_expect_success "Size of $type is correct" '
 	echo $size >expect &&
-	git cat-file -s $oid >actual &&
+	git cat-file -s "$object_name" >actual &&
 	test_cmp expect actual
     '
 
     test -z "$content" ||
     test_expect_success "Content of $type is correct" '
 	echo_without_newline "$content" >expect &&
-	git cat-file $type $oid >actual &&
+	git cat-file $type "$object_name" >actual &&
 	test_cmp expect actual
     '
 
     test_expect_success "Pretty content of $type is correct" '
 	echo_without_newline "$pretty_content" >expect &&
-	git cat-file -p $oid >actual &&
+	git cat-file -p "$object_name" >actual &&
 	test_cmp expect actual
     '
 
     test -z "$content" ||
     test_expect_success "--batch output of $type is correct" '
 	echo "$batch_output" >expect &&
-	echo $oid | git cat-file --batch >actual &&
+	echo "$object_name" | git cat-file --batch >actual &&
 	test_cmp expect actual
     '
 
     test_expect_success "--batch-check output of $type is correct" '
 	echo "$oid $type $size" >expect &&
-	echo_without_newline $oid | git cat-file --batch-check >actual &&
+	echo_without_newline "$object_name" | git cat-file --batch-check >actual &&
 	test_cmp expect actual
     '
 
@@ -168,13 +169,13 @@ $content"
 	test -z "$content" ||
 		test_expect_success "--batch-command $opt output of $type content is correct" '
 		echo "$batch_output" >expect &&
-		test_write_lines "contents $oid" | git cat-file --batch-command $opt >actual &&
+		test_write_lines "contents $object_name" | git cat-file --batch-command $opt >actual &&
 		test_cmp expect actual
 	'
 
 	test_expect_success "--batch-command $opt output of $type info is correct" '
 		echo "$oid $type $size" >expect &&
-		test_write_lines "info $oid" |
+		test_write_lines "info $object_name" |
 		git cat-file --batch-command $opt >actual &&
 		test_cmp expect actual
 	'
@@ -182,19 +183,28 @@ $content"
 
     test_expect_success "custom --batch-check format" '
 	echo "$type $oid" >expect &&
-	echo $oid | git cat-file --batch-check="%(objecttype) %(objectname)" >actual &&
+	echo "$object_name" | git cat-file --batch-check="%(objecttype) %(objectname)" >actual &&
 	test_cmp expect actual
     '
 
     test_expect_success "custom --batch-command format" '
 	echo "$type $oid" >expect &&
-	echo "info $oid" | git cat-file --batch-command="%(objecttype) %(objectname)" >actual &&
+	echo "info $object_name" | git cat-file --batch-command="%(objecttype) %(objectname)" >actual &&
 	test_cmp expect actual
     '
 
-    test_expect_success '--batch-check with %(rest)' '
+    # FIXME: %(rest) is incompatible with object names that include whitespace,
+    # e.g. HEAD:path/to/a/file with spaces. Use the resolved OID as input to
+    # test this instead of the raw object name.
+    if echo "$object_name" | grep " "; then
+	test_rest=test_expect_failure
+    else
+	test_rest=test_expect_success
+    fi
+
+    $test_rest '--batch-check with %(rest)' '
 	echo "$type this is some extra content" >expect &&
-	echo "$oid    this is some extra content" |
+	echo "$object_name    this is some extra content" |
 		git cat-file --batch-check="%(objecttype) %(rest)" >actual &&
 	test_cmp expect actual
     '
@@ -205,7 +215,7 @@ $content"
 		echo "$size" &&
 		echo "$content"
 	} >expect &&
-	echo $oid | git cat-file --batch="%(objectsize)" >actual &&
+	echo "$object_name" | git cat-file --batch="%(objectsize)" >actual &&
 	test_cmp expect actual
     '
 
@@ -215,7 +225,7 @@ $content"
 		echo "$type" &&
 		echo "$content"
 	} >expect &&
-	echo $oid | git cat-file --batch="%(objecttype)" >actual &&
+	echo "$object_name" | git cat-file --batch="%(objecttype)" >actual &&
 	test_cmp expect actual
     '
 }
@@ -230,6 +240,8 @@ test_expect_success "setup" '
 	git config extensions.compatobjectformat $test_compat_hash_algo &&
 	echo_without_newline "$hello_content" > hello &&
 	git update-index --add hello &&
+	echo_without_newline "$hello_content" > "path with spaces" &&
+	git update-index --add --chmod=+x "path with spaces" &&
 	git commit -m "add hello file"
 '
 
@@ -269,13 +281,17 @@ test_expect_success '--batch-check without %(rest) considers whole line' '
 
 tree_oid=$(git write-tree)
 tree_compat_oid=$(git rev-parse --output-object-format=$test_compat_hash_algo $tree_oid)
-tree_size=$(($(test_oid rawsz) + 13))
-tree_compat_size=$(($(test_oid --hash=compat rawsz) + 13))
-tree_pretty_content="100644 blob $hello_oid	hello${LF}"
-tree_compat_pretty_content="100644 blob $hello_compat_oid	hello${LF}"
+tree_size=$((2 * $(test_oid rawsz) + 13 + 24))
+tree_compat_size=$((2 * $(test_oid --hash=compat rawsz) + 13 + 24))
+tree_pretty_content="100644 blob $hello_oid	hello${LF}100755 blob $hello_oid	path with spaces${LF}"
+tree_compat_pretty_content="100644 blob $hello_compat_oid	hello${LF}100755 blob $hello_compat_oid	path with spaces${LF}"
 
 run_tests 'tree' $tree_oid $tree_size "" "$tree_pretty_content"
 run_tests 'tree' $tree_compat_oid $tree_compat_size "" "$tree_compat_pretty_content"
+run_tests 'blob' "$tree_oid:hello" $hello_size "" "$hello_content" $hello_oid
+run_tests 'blob' "$tree_compat_oid:hello" $hello_size "" "$hello_content" $hello_compat_oid
+run_tests 'blob' "$tree_oid:path with spaces" $hello_size "" "$hello_content" $hello_oid
+run_tests 'blob' "$tree_compat_oid:path with spaces" $hello_size "" "$hello_content" $hello_compat_oid
 
 commit_message="Initial commit"
 commit_oid=$(echo_without_newline "$commit_message" | git commit-tree $tree_oid)

-- 
gitgitgadget
Victoria Dye via GitGitGadget· Jun 2, 2025, 18:55 UTC · re: Victoria Dye via GitGitGadget · lore

[PATCH 2/3] cat-file: add %(objectmode) atom

From: Victoria Dye <vdye@github.com>

Add a formatting atom, used with the --batch-check/--batch-command options, that prints the octal representation of the object mode if a given revision includes that information, e.g. one that follows the format <tree-ish>:<path>. If the mode information does not exist, an empty string is printed instead.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Victoria Dye <vdye@github.com>
---
 Documentation/git-cat-file.adoc |  5 +++++
 builtin/cat-file.c              |  9 ++++++--
 t/t1006-cat-file.sh             | 38 +++++++++++++++++++--------------
 3 files changed, 34 insertions(+), 18 deletions(-)
Show changes to 3 files +34 −18

Documentation/git-cat-file.adoc, builtin/cat-file.c, t/t1006-cat-file.sh

diff --git a/Documentation/git-cat-file.adoc b/Documentation/git-cat-file.adoc
index cde79ad242bb..5c002c0499e4 100644
--- a/Documentation/git-cat-file.adoc
+++ b/Documentation/git-cat-file.adoc
@@ -307,6 +307,11 @@ newline. The available atoms are:
 `objecttype`::
 	The type of the object (the same as `cat-file -t` reports).
 
+`objectmode`::
+	If the specified object has mode information (such as a tree or
+	index entry), the mode expressed as an octal integer. Otherwise,
+	empty string.
+
 `objectsize`::
 	The size, in bytes, of the object (the same as `cat-file -s`
 	reports).
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 67a5ff2b9ebd..b11576756bcc 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -275,6 +275,7 @@ struct expand_data {
 	struct object_id oid;
 	enum object_type type;
 	unsigned long size;
+	unsigned short mode;
 	off_t disk_size;
 	const char *rest;
 	struct object_id delta_base_oid;
@@ -306,6 +307,7 @@ struct expand_data {
 	 */
 	unsigned skip_object_info : 1;
 };
+#define EXPAND_DATA_INIT  { .mode = S_IFINVALID }
 
 static int is_atom(const char *atom, const char *s, int slen)
 {
@@ -345,6 +347,9 @@ static int expand_atom(struct strbuf *sb, const char *atom, int len,
 		else
 			strbuf_addstr(sb,
 				      oid_to_hex(&data->delta_base_oid));
+	} else if (is_atom("objectmode", atom, len)) {
+		if (!data->mark_query && !(S_IFINVALID == data->mode))
+			strbuf_addf(sb, "%06o", data->mode);
 	} else
 		return 0;
 	return 1;
@@ -613,6 +618,7 @@ static void batch_one_object(const char *obj_name,
 		goto out;
 	}
 
+	data->mode = ctx.mode;
 	batch_object_write(obj_name, scratch, opt, data, NULL, 0);
 
 out:
@@ -866,7 +872,7 @@ static int batch_objects(struct batch_options *opt)
 {
 	struct strbuf input = STRBUF_INIT;
 	struct strbuf output = STRBUF_INIT;
-	struct expand_data data;
+	struct expand_data data = EXPAND_DATA_INIT;
 	int save_warning;
 	int retval = 0;
 
@@ -875,7 +881,6 @@ static int batch_objects(struct batch_options *opt)
 	 * object_info to be handed to oid_object_info_extended for each
 	 * object.
 	 */
-	memset(&data, 0, sizeof(data));
 	data.mark_query = 1;
 	expand_format(&output,
 		      opt->format ? opt->format : DEFAULT_FORMAT,
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 7c9512a6b439..97052b3f31f1 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -114,10 +114,11 @@ strlen () {
 run_tests () {
     type=$1
     object_name="$2"
-    size=$3
-    content=$4
-    pretty_content=$5
-    oid=${6:-"$object_name"}
+    mode=$3
+    size=$4
+    content=$5
+    pretty_content=$6
+    oid=${7:-"$object_name"}
 
     batch_output="$oid $type $size
 $content"
@@ -209,6 +210,12 @@ $content"
 	test_cmp expect actual
     '
 
+    test_expect_success '--batch-check with %(objectmode)' '
+	echo "$mode $oid" >expect &&
+	echo $object_name | git cat-file --batch-check="%(objectmode) %(objectname)" >actual &&
+	test_cmp expect actual
+    '
+
     test -z "$content" ||
     test_expect_success "--batch without type ($type)" '
 	{
@@ -247,8 +254,7 @@ test_expect_success "setup" '
 
 run_blob_tests () {
     oid=$1
-
-    run_tests 'blob' $oid $hello_size "$hello_content" "$hello_content"
+    run_tests 'blob' $oid "" $hello_size "$hello_content" "$hello_content"
 
     test_expect_success '--batch-command --buffer with flush for blob info' '
 	echo "$oid blob $hello_size" >expect &&
@@ -286,12 +292,12 @@ tree_compat_size=$((2 * $(test_oid --hash=compat rawsz) + 13 + 24))
 tree_pretty_content="100644 blob $hello_oid	hello${LF}100755 blob $hello_oid	path with spaces${LF}"
 tree_compat_pretty_content="100644 blob $hello_compat_oid	hello${LF}100755 blob $hello_compat_oid	path with spaces${LF}"
 
-run_tests 'tree' $tree_oid $tree_size "" "$tree_pretty_content"
-run_tests 'tree' $tree_compat_oid $tree_compat_size "" "$tree_compat_pretty_content"
-run_tests 'blob' "$tree_oid:hello" $hello_size "" "$hello_content" $hello_oid
-run_tests 'blob' "$tree_compat_oid:hello" $hello_size "" "$hello_content" $hello_compat_oid
-run_tests 'blob' "$tree_oid:path with spaces" $hello_size "" "$hello_content" $hello_oid
-run_tests 'blob' "$tree_compat_oid:path with spaces" $hello_size "" "$hello_content" $hello_compat_oid
+run_tests 'tree' $tree_oid "" $tree_size "" "$tree_pretty_content"
+run_tests 'tree' $tree_compat_oid "" $tree_compat_size "" "$tree_compat_pretty_content"
+run_tests 'blob' "$tree_oid:hello" "100644" $hello_size "" "$hello_content" $hello_oid
+run_tests 'blob' "$tree_compat_oid:hello" "100644" $hello_size "" "$hello_content" $hello_compat_oid
+run_tests 'blob' "$tree_oid:path with spaces" "100755" $hello_size "" "$hello_content" $hello_oid
+run_tests 'blob' "$tree_compat_oid:path with spaces" "100755" $hello_size "" "$hello_content" $hello_compat_oid
 
 commit_message="Initial commit"
 commit_oid=$(echo_without_newline "$commit_message" | git commit-tree $tree_oid)
@@ -310,8 +316,8 @@ committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
 
 $commit_message"
 
-run_tests 'commit' $commit_oid $commit_size "$commit_content" "$commit_content"
-run_tests 'commit' $commit_compat_oid $commit_compat_size "$commit_compat_content" "$commit_compat_content"
+run_tests 'commit' $commit_oid "" $commit_size "$commit_content" "$commit_content"
+run_tests 'commit' $commit_compat_oid "" $commit_compat_size "$commit_compat_content" "$commit_compat_content"
 
 tag_header_without_oid="type blob
 tag hellotag
@@ -334,8 +340,8 @@ tag_size=$(strlen "$tag_content")
 tag_compat_oid=$(git rev-parse --output-object-format=$test_compat_hash_algo $tag_oid)
 tag_compat_size=$(strlen "$tag_compat_content")
 
-run_tests 'tag' $tag_oid $tag_size "$tag_content" "$tag_content"
-run_tests 'tag' $tag_compat_oid $tag_compat_size "$tag_compat_content" "$tag_compat_content"
+run_tests 'tag' $tag_oid "" $tag_size "$tag_content" "$tag_content"
+run_tests 'tag' $tag_compat_oid "" $tag_compat_size "$tag_compat_content" "$tag_compat_content"
 
 test_expect_success "Reach a blob from a tag pointing to it" '
 	echo_without_newline "$hello_content" >expect &&

-- 
gitgitgadget
Jeff King· Jun 4, 2025, 19:36 UTC · re: Victoria Dye via GitGitGadget · lore

Re: [PATCH 2/3] cat-file: add %(objectmode) atom

On Mon, Jun 02, 2025 at 06:55:54PM +0000, Victoria Dye via GitGitGadget wrote:
Show 5 quoted lines
> Add a formatting atom, used with the --batch-check/--batch-command options,
> that prints the octal representation of the object mode if a given revision
> includes that information, e.g. one that follows the format
> <tree-ish>:<path>. If the mode information does not exist, an empty string
> is printed instead.

Overall, this looks good to me. I have a few small comments below, though I'm not sure if they merit a re-roll or not.

Show 10 quoted lines
> @@ -345,6 +347,9 @@ static int expand_atom(struct strbuf *sb, const char *atom, int len,
>  		else
>  			strbuf_addstr(sb,
>  				      oid_to_hex(&data->delta_base_oid));
> +	} else if (is_atom("objectmode", atom, len)) {
> +		if (!data->mark_query && !(S_IFINVALID == data->mode))
> +			strbuf_addf(sb, "%06o", data->mode);
>  	} else
>  		return 0;
>  	return 1;
Looking at this hunk raised a few questions. Fortunately with answers. ;)

First, in other parts of this if/else chain, when mark_query is set we need to perform some action (usually setting up the object_info pointers). But we _don't_ need to do that here, since we get the mode info "for free" from get_oid_with_context(). Good.

Second, how do we reliably get S_IFINVALID? We can see that the expand_data struct is now initialized with it:

> +#define EXPAND_DATA_INIT  { .mode = S_IFINVALID }

But that seems like it would be a bug, since we only initialize it once, in batch_objects():

Show 20 quoted lines
> @@ -866,7 +872,7 @@ static int batch_objects(struct batch_options *opt)
>  {
>  	struct strbuf input = STRBUF_INIT;
>  	struct strbuf output = STRBUF_INIT;
> -	struct expand_data data;
> +	struct expand_data data = EXPAND_DATA_INIT;
>  	int save_warning;
>  	int retval = 0;
>  
> @@ -875,7 +881,6 @@ static int batch_objects(struct batch_options *opt)
>  	 * object_info to be handed to oid_object_info_extended for each
>  	 * object.
>  	 */
> -	memset(&data, 0, sizeof(data));
>  	data.mark_query = 1;
>  	expand_format(&output,
>  		      opt->format ? opt->format : DEFAULT_FORMAT,
>  
>  static int is_atom(const char *atom, const char *s, int slen)
>  {

...and then call batch_one_object() over and over. So at first glance, doing this:

  (echo HEAD:Makefile; echo HEAD) |
  git cat-file --batch-check='%(objectmode)'

would let the mode from the first object bleed over into the second. But that doesn't happen, because we overwrite expand_data.mode for each object unconditionally, here:

Show 8 quoted lines
> @@ -613,6 +618,7 @@ static void batch_one_object(const char *obj_name,
>  		goto out;
>  	}
>  
> +	data->mode = ctx.mode;
>  	batch_object_write(obj_name, scratch, opt, data, NULL, 0);
>  
>  out:

And there we are relying on ctx.mode, which we get from get_oid_with_context(), which always falls back to S_IFINVALID if no mode is available. Good.

But I think that means that the value set in EXPAND_DATA_INIT is never used, and we could continue to zero-initialize the struct with memset?

That said, it's probably OK to err on the side of over-initializing. The worst case is probably somebody later reading the code being confused about the importance of the line. And at best it may prevent a future code path from unexpectedly reading a funny value.

And on to the third question. In the non-batch code path of cat_one_file(), we do:

          if (obj_context.mode == S_IFINVALID)
                  obj_context.mode = 0100644;

which made me wonder if we should be harmonizing our behavior. But that mode is used only for passing to filter_object() and textconv_object(). Neither of which really care about the mode, and this is mostly just saying "eh, do your regular thing as if it were a blob we found at --path". I suspect we could get the same effect by just passing a hard-coded 100644 to those functions, but probably not worth changing now (and certainly very orthogonal to your patch). But the important thing is we do not really need to worry about being consistent with this line. Good.

-Peff
Victoria Dye via GitGitGadget· Jun 2, 2025, 18:55 UTC · re: Victoria Dye via GitGitGadget · lore

[PATCH 3/3] cat-file.c: add batch handling for submodules

From: Victoria Dye <vdye@github.com>

When an object specification is passed to 'cat-file --batch[-check]' referring to a submodule (e.g. 'HEAD:path/to/my/submodule'), the current behavior of the command is to print the "missing" error message. However, it is often valuable for callers to distinguish between paths that are actually missing and "the submodule tree entry exists, but the object does not exist in the repository".

To disambiguate without needing to invoke a separate Git process (e.g. 'ls-tree'), print the message "<oid> submodule" for such objects instead of "<object> missing". In addition to the change from "missing" to "submodule", the new message differs from the old in that it always prints the resolved tree entry's OID, rather than the input object specification.

Note that this implementation maintains a distinction between submodules where the commit OID is not present in the repo, and submodules where the commit OID *is* present; the former will now print "<object> submodule", but the latter will still print the full object content.

Signed-off-by: Victoria Dye <vdye@github.com>
---
 Documentation/git-cat-file.adoc |  8 ++++++++
 builtin/cat-file.c              |  5 ++++-
 t/t1006-cat-file.sh             | 25 +++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)
Show changes to 3 files +37 −1

Documentation/git-cat-file.adoc, builtin/cat-file.c, t/t1006-cat-file.sh

diff --git a/Documentation/git-cat-file.adoc b/Documentation/git-cat-file.adoc
index 5c002c0499e4..180d1ad363fd 100644
--- a/Documentation/git-cat-file.adoc
+++ b/Documentation/git-cat-file.adoc
@@ -373,6 +373,14 @@ If a name is specified that might refer to more than one object (an ambiguous sh
 <object> SP ambiguous LF
 ------------
 
+If a name is specified that refers to a submodule entry in a tree and the
+target object does not exist in the repository, then `cat-file` will ignore
+any custom format and print (with the object ID of the submodule):
+
+------------
+<oid> SP submodule LF
+------------
+
 If `--follow-symlinks` is used, and a symlink in the repository points
 outside the repository, then `cat-file` will ignore any custom format
 and print:
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index b11576756bcc..4b23fcecbd8e 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -496,7 +496,10 @@ static void batch_object_write(const char *obj_name,
 						       &data->oid, &data->info,
 						       OBJECT_INFO_LOOKUP_REPLACE);
 		if (ret < 0) {
-			report_object_status(opt, obj_name, &data->oid, "missing");
+			if (data->mode == S_IFGITLINK)
+				report_object_status(opt, oid_to_hex(&data->oid), &data->oid, "submodule");
+			else
+				report_object_status(opt, obj_name, &data->oid, "missing");
 			return;
 		}
 
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 97052b3f31f1..f123ef1e360a 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -1220,6 +1220,31 @@ test_expect_success 'cat-file --batch-check respects replace objects' '
 	test_cmp expect actual
 '
 
+test_expect_success 'batch-check with a submodule' '
+	# FIXME: this call to mktree is incompatible with compatObjectFormat
+	# because the submodule OID cannot be mapped to the compat hash algo.
+	test_unconfig extensions.compatobjectformat &&
+	printf "160000 commit $(test_oid deadbeef)\tsub\n" >tree-with-sub &&
+	tree=$(git mktree <tree-with-sub) &&
+	test_config extensions.compatobjectformat $test_compat_hash_algo &&
+
+	git cat-file --batch-check >actual <<-EOF &&
+	$tree:sub
+	EOF
+	printf "$(test_oid deadbeef) submodule\n" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'batch-check with a submodule, object exists' '
+	printf "160000 commit $commit_oid\tsub\n" >tree-with-sub &&
+	tree=$(git mktree <tree-with-sub) &&
+	git cat-file --batch-check >actual <<-EOF &&
+	$tree:sub
+	EOF
+	printf "$commit_oid commit $commit_size\n" >expect &&
+	test_cmp expect actual
+'
+
 # Pull the entry for object with oid "$1" out of the output of
 # "cat-file --batch", including its object content (which requires
 # parsing and reading a set amount of bytes, hence perl).

-- 
gitgitgadget
Jeff King· Jun 4, 2025, 19:54 UTC · re: Victoria Dye via GitGitGadget · lore

Re: [PATCH 3/3] cat-file.c: add batch handling for submodules

On Mon, Jun 02, 2025 at 06:55:55PM +0000, Victoria Dye via GitGitGadget wrote:
Show 5 quoted lines
> To disambiguate without needing to invoke a separate Git process (e.g.
> 'ls-tree'), print the message "<oid> submodule" for such objects instead of
> "<object> missing". In addition to the change from "missing" to "submodule",
> the new message differs from the old in that it always prints the resolved
> tree entry's OID, rather than the input object specification.

OK. I read over the discussion from last year, which I think mostly centered around this patch. I do still think in the long run it would be nice for cat-file to produce what output it _can_ for a missing object (e.g., the oid and mode).

But I think it is OK to punt on that for now. Because "<oid> missing" lines already exist, we'd probably need to put such behavior behind a new command-line option. So while "<oid> submodule" lines would be unnecessary in that hypothetical future world, we are not digging the hole any deeper, from a backwards-compatibility standpoint.

Although speaking of backwards compatibility, I guess older readers may be surprised that the old "missing" message becomes a "submodule" one. They may need to be updated if they were written carefully to bail on unknown input (and were happy seeing "missing" messages for submodules). So there may be some fallout, but it's not like the existing messages were particularly useful in the first place.

> Note that this implementation maintains a distinction between submodules
> where the commit OID is not present in the repo, and submodules where the
> commit OID *is* present; the former will now print "<object> submodule", but
> the latter will still print the full object content.

Hmm, that is an interesting point. It feels kind of arbitrary, but I'm having trouble making a strong argument for one direction or the other. The way you've written it means that readers need to be prepared to parse _both_ the mode and "<oid> submodule" lines to find submodules. But maybe there's some value in finding out more information about submodule commits you do have in-repo.

The implementations are similar. Replacing this hunk:
Show 16 quoted lines
> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index b11576756bcc..4b23fcecbd8e 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -496,7 +496,10 @@ static void batch_object_write(const char *obj_name,
>  						       &data->oid, &data->info,
>  						       OBJECT_INFO_LOOKUP_REPLACE);
>  		if (ret < 0) {
> -			report_object_status(opt, obj_name, &data->oid, "missing");
> +			if (data->mode == S_IFGITLINK)
> +				report_object_status(opt, oid_to_hex(&data->oid), &data->oid, "submodule");
> +			else
> +				report_object_status(opt, obj_name, &data->oid, "missing");
>  			return;
>  		}
>  
with:
Show changes to builtin/cat-file.c +5 −1
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 4b23fcecbd..1b200e1607 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -488,6 +488,11 @@ static void batch_object_write(const char *obj_name,
 		if (opt->objects_filter.choice == LOFC_BLOB_LIMIT)
 			data->info.sizep = &data->size;
 
+		if (data->mode == S_IFGITLINK) {
+			report_object_status(opt, oid_to_hex(&data->oid), &data->oid, "submodule");
+			return;
+		}
+
 		if (pack)
 			ret = packed_object_info(the_repository, pack, offset,
 						 &data->info);

so I think the decision is really about what people will find most
useful. So I dunno. It is mostly a coin-flip, leading me to say that
what you picked just came up "heads" and is good enough. ;)

-Peff
Victoria Dye· Jun 5, 2025, 00:12 UTC · re: Jeff King · lore

Re: [PATCH 3/3] cat-file.c: add batch handling for submodules

Jeff King wrote:
Show 12 quoted lines
> On Mon, Jun 02, 2025 at 06:55:55PM +0000, Victoria Dye via GitGitGadget wrote:
> 
>> To disambiguate without needing to invoke a separate Git process (e.g.
>> 'ls-tree'), print the message "<oid> submodule" for such objects instead of
>> "<object> missing". In addition to the change from "missing" to "submodule",
>> the new message differs from the old in that it always prints the resolved
>> tree entry's OID, rather than the input object specification.
> 
> OK. I read over the discussion from last year, which I think mostly
> centered around this patch. I do still think in the long run it would be
> nice for cat-file to produce what output it _can_ for a missing object
> (e.g., the oid and mode).
One way to handle that could be changing the message to something like:
submodule SP <mode> SP <oid>
but...
Show 13 quoted lines
> 
> But I think it is OK to punt on that for now. Because "<oid> missing"
> lines already exist, we'd probably need to put such behavior behind a
> new command-line option. So while "<oid> submodule" lines would be
> unnecessary in that hypothetical future world, we are not digging the
> hole any deeper, from a backwards-compatibility standpoint.
> 
> Although speaking of backwards compatibility, I guess older readers may
> be surprised that the old "missing" message becomes a "submodule" one.
> They may need to be updated if they were written carefully to bail on
> unknown input (and were happy seeing "missing" messages for submodules).
> So there may be some fallout, but it's not like the existing messages
> were particularly useful in the first place.

...I suspect that'd be even less compatible with existing automation around 'cat-file' than just swapping out "submodule" for "missing", and users can theoretically infer that the mode is 160000 (S_IFGITLINK). That said, if at some point in the future we support submodules with a different mode, then an explicit value would be fairly useful.

Happy to change it or keep it the same, I have no strong preference either way.

Show 12 quoted lines
> 
>> Note that this implementation maintains a distinction between submodules
>> where the commit OID is not present in the repo, and submodules where the
>> commit OID *is* present; the former will now print "<object> submodule", but
>> the latter will still print the full object content.
> 
> Hmm, that is an interesting point. It feels kind of arbitrary, but I'm
> having trouble making a strong argument for one direction or the other.
> The way you've written it means that readers need to be prepared to
> parse _both_ the mode and "<oid> submodule" lines to find submodules.
> But maybe there's some value in finding out more information about
> submodule commits you do have in-repo.

This was pretty much my thought process on it. It was a somewhat arbitrary choice, but what tipped me towards distinguishing the cases is that I'd rather have information like size, content, etc. about a commit and not need to use it, than need it but not have it available. That, and it does maintain the existing treatment of self-referential submodules.

Jeff King· Jun 5, 2025, 07:51 UTC · re: Victoria Dye · lore

Re: [PATCH 3/3] cat-file.c: add batch handling for submodules

On Wed, Jun 04, 2025 at 05:12:54PM -0700, Victoria Dye wrote:
Show 8 quoted lines
> > OK. I read over the discussion from last year, which I think mostly
> > centered around this patch. I do still think in the long run it would be
> > nice for cat-file to produce what output it _can_ for a missing object
> > (e.g., the oid and mode).
> 
> One way to handle that could be changing the message to something like:
> 
> submodule SP <mode> SP <oid>

Hmm, yeah. That seemed weird to me at first because it doesn't necessarily match what the caller asked for via batch-check. But really, mode and oid are the only reasonable things we could report anyway[1]. And the mode is implicit in the word "submodule", so really there is only the oid to report.

[1] For now, at least. If we ever finally unify all of the various
    formatting code, then one might in theory be able to feed a refname
    to cat-file and print information about the ref, or perhaps other
    meta-information. But let's not worry about that hypothetical for
    now.
Show 8 quoted lines
> ...I suspect that'd be even less compatible with existing automation around
> 'cat-file' than just swapping out "submodule" for "missing", and users can
> theoretically infer that the mode is 160000 (S_IFGITLINK). That said, if at
> some point in the future we support submodules with a different mode, then
> an explicit value would be fairly useful.
> 
> Happy to change it or keep it the same, I have no strong preference either
> way.
Right, that makes sense. I do wonder if:
  <oid> missing submodule

might be friendlier to readers who are matching on /^[0-9a-f]+ missing/, but now I am just guessing at a hypothetical program. So it may not be worth going down that rabbit hole, and we can just go with what you posted.

We can always worry about extending it later with an option to say "turn placeholders for missing objects into empty strings" or similar.

I did come across one other interesting case while thinking about this, though. When running:

  git cat-file --batch-check='%(objectname) %(objectmode)'

we do not need to access the object at all! So why does a submodule entry cause us to complain? The answer is that cat-file will (mostly for historical reasons) confirm the existence of the object name that is fed to it by calling oid_object_info(). The only exception is when we are doing --batch-all-objects, since there we know we have the object, because we found it by iterating the odb. And we optimize out the extra call for that case (which makes a big difference if you're just printing the object names).

But since we don't expect submodule entries to exist in the first place, it might be reasonable to loosen that check. Something like this, though I think it could benefit from some refactoring:

Show changes to builtin/cat-file.c +20 −2
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 4b23fcecbd..bb52d9b673 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -304,8 +304,20 @@ struct expand_data {
 	 * This flag will be true if the requested batch format and options
 	 * don't require us to call oid_object_info, which can then be
 	 * optimized out.
+	 *
+	 * The "submodule" variant is true if the format doesn't require it,
+	 * but other options mean we'd usually continue to do so to check
+	 * object existence. We can still omit the call for submodules in that
+	 * case.
+	 *
+	 * This might be less confusing if we break skip_object_info down into
+	 * two parts:
+	 *   - does the format require oid_object_info?
+	 *   - do the other options require checking existence?
 	 */
 	unsigned skip_object_info : 1;
+	unsigned skip_submodule_info : 1;
+
 };
 #define EXPAND_DATA_INIT  { .mode = S_IFINVALID }
 
@@ -477,7 +489,8 @@ static void batch_object_write(const char *obj_name,
 			       struct packed_git *pack,
 			       off_t offset)
 {
-	if (!data->skip_object_info) {
+	if (!(data->skip_object_info ||
+	      (data->skip_submodule_info && data->mode == S_IFGITLINK))) {
 		int ret;
 
 		if (use_mailmap ||
@@ -939,6 +952,12 @@ static int batch_objects(struct batch_options *opt)
 
 		strbuf_release(&output);
 		return 0;
+	} else {
+		struct object_info empty = OBJECT_INFO_INIT;
+
+		if (!memcmp(&data.info, &empty, sizeof(empty)) &&
+		    opt->objects_filter.choice == LOFC_DISABLED)
+			data.skip_submodule_info = 1;
 	}
 
 	/*

I don't think that needs to be part of your series, though. We'd still
potentially need to handle the missing-submodule case for format
requests that actually look at the object, which would hit the "<oid>
submodule" case you're adding. So it could come later (or not at all),
and it's probably only worth pursuing if it would make life easier for
your intended caller.

-Peff
Junio C Hamano· Jun 4, 2025, 14:43 UTC · re: Victoria Dye via GitGitGadget · lore

Re: [PATCH 0/3] cat-file: add %(objectmode) and submodule message to batch commands

"Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com> writes:
Show 20 quoted lines
> This series re-attempts the changes proposed last year [1] for extending the
> information about tree entries available from the 'cat-file' batch format
> commands. It also (hopefully) addresses the initial round of feedback that
> series received.
>
> The first patch updates 't1006-cat-file.sh' to test non-OID object
> specifications. In response to the feedback in [2], I added more careful
> quoting and a couple tests using paths with spaces. This change revealed a
> (likely known) limitation of the '%(rest)' atom when processing object names
> with spaces. To make that limitation explicit, I marked the relevant test as
> expected to fail.
>
> The second patch adds "mode" support. This is essentially unchanged from its
> initial submission, save for some conflict resolution in the test script.
>
> The final patch takes a different approach to submodule resolution than the
> initial submission; rather than treat the entry as a "regular" commit object
> with empty content, we now print an error message similar to the "missing",
> "ambiguous", etc. cases, but with the tree entry's OID rather than the input
> object name.

I did not send any line-by-line reviews, but after reading these patches I didn't see anything questionable. Unless we see others comments that need to be addressed, let's merge it to 'next' in preparation for the next cycle.

Thanks.
Jeff King· Jun 4, 2025, 19:57 UTC · re: Junio C Hamano · lore

Re: [PATCH 0/3] cat-file: add %(objectmode) and submodule message to batch commands

On Wed, Jun 04, 2025 at 07:43:21AM -0700, Junio C Hamano wrote:
Show 10 quoted lines
> > The final patch takes a different approach to submodule resolution than the
> > initial submission; rather than treat the entry as a "regular" commit object
> > with empty content, we now print an error message similar to the "missing",
> > "ambiguous", etc. cases, but with the tree entry's OID rather than the input
> > object name.
> 
> I did not send any line-by-line reviews, but after reading these
> patches I didn't see anything questionable.  Unless we see others
> comments that need to be addressed, let's merge it to 'next' in
> preparation for the next cycle.

I left a more detailed review. But it's mostly musing and self-answering questions. I'd be OK to see this progress as-is.

-Peff

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