Subject: Re: [PATCH v2 1/2] cat-file: add mailmap support to -s option

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Mon, 26 Sep 2022 15:16:57 +0200

On Mon, Sep 26 2022, Siddharth Asthana wrote:

> Even though the cat-file command with `-s` option does not complain when
> `--use-mailmap` option is given, the latter option is ignored. Compute
> the size of the object after replacing the idents and report it instead.
>
> In order to make `-s` option honour the mailmap mechanism we have to
> read the contents of the commit/tag object. Make use of the call to
> `oid_object_info_extended()` to get the contents of the object and store
> in `buf`. `buf` is later freed in the function.
>
> Mentored-by: Christian Couder <[email-masked]>
> Mentored-by: John Cai <[email-masked]>
> Signed-off-by: Siddharth Asthana <[email-masked]>
> ---
>  Documentation/git-cat-file.txt |  4 +++-
>  builtin/cat-file.c             | 13 +++++++++++++
>  t/t4203-mailmap.sh             | 10 ++++++++++
>  3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/git-cat-file.txt b/Documentation/git-cat-file.txt
> index ec30b5c574..594b6f2dfd 100644
> --- a/Documentation/git-cat-file.txt
> +++ b/Documentation/git-cat-file.txt
> @@ -45,7 +45,9 @@ OPTIONS
>  
>  -s::
>  	Instead of the content, show the object size identified by
> -	`<object>`.
> +	`<object>`. If used with `--use-mailmap` option, will show the
> +	size of updated object after replacing idents using the mailmap
> +	mechanism.
>  
>  -e::
>  	Exit with zero status if `<object>` exists and is a valid
> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index 989eee0bb4..9942b93867 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -132,8 +132,21 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
>  
>  	case 's':
>  		oi.sizep = &size;
> +
> +		if (use_mailmap) {
> +			oi.typep = &type;
> +			oi.contentp = (void**)&buf;
> +		}
> +
>  		if (oid_object_info_extended(the_repository, &oid, &oi, flags) < 0)
>  			die("git cat-file: could not get object info");
> +
> +		if (use_mailmap && (type == OBJ_COMMIT || type == OBJ_TAG)) {
> +			size_t s = size;
> +			buf = replace_idents_using_mailmap(buf, &s);

This is partially commentary on your already-landed series for cat-file
--mailmap support. I wondered why we needed this temporary variable, and
why we needed the cast_size_t_to_ulong() at all. On "master" we have a
size, but e.g. for cat_one_file()'s *current* codpaths we just pass it
to write_or_die().

So the net effect is that we refuse to use write_or_die() if the number
in size_t doesn't fit an unsigned long, even though we never need an
unsigned long in that case.

We have *other* things in the object code that need unsigned long, so it
probably amounts to no practical limitation, but it's confusing & I
think per [1] below we could do away with it.

There's also a subtle gotcha on "master", we
replace_idents_using_mailmap() with a possibly NULL "contents", which is
a misuse of the strbuf API (the "buf" member should never be NULL), but
we're about to die anyway...

> +			size = cast_size_t_to_ulong(s);
> +		}
> +
>  		printf("%"PRIuMAX"\n", (uintmax_t)size);

...but expanding on "master", here we have seemingly the first use of
cast_size_t_to_ulong() thaht's actually needed in this file. I.e. we are
about to use PRIuMAX.

But why not skip the cast(s) and make this more obvious by having the
printf() argument be cast_size_t_to_ulong(size)?

In your 2/2 you then have another use of cast_size_t_to_ulong() which
*is* needed in that case (we're about to stick it in a "unsigned long"
member, and the "size_t s" temporary variable is also needed in that
case.

1.

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 989eee0bb4c..676c34cba4b 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -178,11 +178,8 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 		if (!buf)
 			die("Cannot read object %s", obj_name);
 
-		if (use_mailmap) {
-			size_t s = size;
-			buf = replace_idents_using_mailmap(buf, &s);
-			size = cast_size_t_to_ulong(s);
-		}
+		if (use_mailmap)
+			buf = replace_idents_using_mailmap(buf, &size);
 
 		/* otherwise just spit out the data */
 		break;
@@ -218,11 +215,8 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 		buf = read_object_with_reference(the_repository, &oid,
 						 exp_type_id, &size, NULL);
 
-		if (use_mailmap) {
-			size_t s = size;
-			buf = replace_idents_using_mailmap(buf, &s);
-			size = cast_size_t_to_ulong(s);
-		}
+		if (use_mailmap)
+			buf = replace_idents_using_mailmap(buf, &size);
 		break;
 	}
 	default:
@@ -391,12 +385,8 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 
 		contents = read_object_file(oid, &type, &size);
 
-		if (use_mailmap) {
-			size_t s = size;
-			contents = replace_idents_using_mailmap(contents, &s);
-			size = cast_size_t_to_ulong(s);
-		}
-
+		if (use_mailmap)
+			contents = replace_idents_using_mailmap(contents, &size);
 		if (!contents)
 			die("object %s disappeared", oid_to_hex(oid));
 		if (type != data->type)