Re: [PATCH v9 3/5] cat-file: teach cat-file a '--allow-unknown-type' option

> Currently 'git cat-file' throws an error while trying to
> print the type or size of a broken/corrupt object. This is
> because these objects are usually of unknown types.
>
> Teach git cat-file a '--allow-unkown-type' option where it prints
> the type or size of a broken/corrupt object without throwing
> an error.

> Modify '-t' and '-s' options to call sha1_object_info_extended()
> directly to support the '--allow-unkown-type' option.
>
> Helped-by: Junio C Hamano <gitster@pobox.com>
> Helped-by: Eric Sunshine <sunshine@sunshineco.com>
> Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
> ---
>  builtin/cat-file.c | 38 ++++++++++++++++++++++++++------------
>  1 file changed, 26 insertions(+), 12 deletions(-)
>
> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index 53b5376..299e2e5 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -9,13 +9,20 @@
>  #include "userdiff.h"
>  #include "streaming.h"
>  
> -static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
> +static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
> +			int unkown_type)
>  {
>  	unsigned char sha1[20];
>  	enum object_type type;
>  	char *buf;
>  	unsigned long size;
>  	struct object_context obj_context;
> +	struct object_info oi = {NULL};
> +	struct strbuf sb = STRBUF_INIT;
> +	unsigned flags = LOOKUP_REPLACE_OBJECT;
> +
> +	if (unkown_type)
> +		flags |= LOOKUP_UNKNOWN_OBJECT;
>  
>  	if (get_sha1_with_context(obj_name, 0, sha1, &obj_context))
>  		die("Not a valid object name %s", obj_name);
> @@ -23,20 +30,22 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
>  	buf = NULL;
>  	switch (opt) {
>  	case 't':
> -		type = sha1_object_info(sha1, NULL);
> -		if (type > 0) {
> -			printf("%s\n", typename(type));
> +		oi.typename = &sb;
> +		if (sha1_object_info_extended(sha1, &oi, flags) < 0)
> +			die("git cat-file: could not get object info");
> +		if (sb.len) {
> +			printf("%s\n", sb.buf);
> +			strbuf_release(&sb);
>  			return 0;
>  		}
>  		break;
>  
>  	case 's':
> -		type = sha1_object_info(sha1, &size);
> -		if (type > 0) {
> -			printf("%lu\n", size);
> -			return 0;
> -		}
> -		break;
> +		oi.sizep = &size;
> +		if (sha1_object_info_extended(sha1, &oi, flags) < 0)
> +			die("git cat-file: could not get object info");
> +		printf("%lu\n", size);
> +		return 0;
>  
>  	case 'e':
>  		return !has_sha1_file(sha1);
> @@ -323,7 +332,7 @@ static int batch_objects(struct batch_options *opt)
>  }
>  
>  static const char * const cat_file_usage[] = {
> -	N_("git cat-file (-t | -s | -e | -p | <type> | --textconv) <object>"),
> +	N_("git cat-file (-t [--allow-unkown-type]|-s [--allow-unkown-type]|-e|-p|<type>|--textconv) <object>"),
>  	N_("git cat-file (--batch | --batch-check) < <list-of-objects>"),
>  	NULL
>  };
> @@ -359,6 +368,7 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
>  	int opt = 0;
>  	const char *exp_type = NULL, *obj_name = NULL;
>  	struct batch_options batch = {0};
> +	int unkown_type = 0;
>  
>  	const struct option options[] = {
>  		OPT_GROUP(N_("<type> can be one of: blob, tree, commit, tag")),
> @@ -369,6 +379,8 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
>  		OPT_CMDMODE('p', NULL, &opt, N_("pretty-print object's content"), 'p'),
>  		OPT_CMDMODE(0, "textconv", &opt,
>  			    N_("for blob objects, run textconv on object's content"), 'c'),
> +		OPT_BOOL( 0, "allow-unkown-type", &unkown_type,
> +			  N_("allow -s and -t to work with broken/corrupt objects")),
>  		{ OPTION_CALLBACK, 0, "batch", &batch, "format",
>  			N_("show info and content of objects fed from the standard input"),
>  			PARSE_OPT_OPTARG, batch_option_callback },
> @@ -402,5 +414,7 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
>  	if (batch.enabled)
>  		return batch_objects(&batch);
>  
> -	return cat_one_file(opt, exp_type, obj_name);
> +	if (unkown_type && opt != 't' && opt != 's')
> +		die("git cat-file --allow-unkown-type: use with -s or -t");
> +	return cat_one_file(opt, exp_type, obj_name, unkown_type);
>  }