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From: Junio C Hamano <gitster@pobox.com>
To: "brian m. carlson" <sandals@crustytoothpaste.net>
Cc: <git@vger.kernel.org>, Jonathan Tan <jonathantanmy@google.com>
Subject: Re: [PATCH 27/44] builtin/show-index: provide options to determine hash algo
Date: Mon, 18 May 2020 09:20:22 -0700	[thread overview]
Message-ID: <xmqqimgt5i61.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <20200513005424.81369-28-sandals@crustytoothpaste.net> (brian m. carlson's message of "Wed, 13 May 2020 00:54:07 +0000")

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> It's possible to use a variety of index formats with show-index, and we
> need a way to indicate the hash algorithm which is in use for a
> particular index we'd like to show.  Default to using the value for the
> repository we're in by calling setup_git_directory_gently, and allow
> overriding it by using a --hash argument.

I think you meant to say that "show-index" does not autodetect what
hash algorithm is used from its input, and the new argument is a way
for the user to help the command when the hash algorithm is
different from what is used in the current repository?

I ask because I found that your version can be read to say that
"show-index" can show the contents of a given pack index using any
hash algorithm we support, and the user can specify --hash=SHA-256
when running the command on a pack .idx that uses SHA-1 object names
to auto-convert it, and readers wouldn't be able to guess which was
meant with only the above five lines.

> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  builtin/show-index.c | 29 ++++++++++++++++++++++++-----
>  git.c                |  2 +-
>  2 files changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/builtin/show-index.c b/builtin/show-index.c
> index 0826f6a5a2..ebfa2e9abd 100644
> --- a/builtin/show-index.c
> +++ b/builtin/show-index.c
> @@ -1,9 +1,12 @@
>  #include "builtin.h"
>  #include "cache.h"
>  #include "pack.h"
> +#include "parse-options.h"
>  
> -static const char show_index_usage[] =
> -"git show-index";
> +static const char *const show_index_usage[] = {
> +	"git show-index [--hash=HASH]",
> +	NULL
> +};

Do we say --hash=SHA-1 etc. or --hash-algo=SHA-256 in other places?
Would the word "hash" alone clear enough that it does not refer to
a specific "hash" value but the name of an algorithm?

The generating side seems to use "index-pack --object-format=<algo>"
and the transport seems to use a capability "object-format=<algo>",
neither of which is directly visible to the end users, but I think
they follow "git init --object-format=<algo>", so we are consistent
there.

Perhaps we should follow suit here, too?

>  int cmd_show_index(int argc, const char **argv, const char *prefix)
>  {
> @@ -11,10 +14,26 @@ int cmd_show_index(int argc, const char **argv, const char *prefix)
>  	unsigned nr;
>  	unsigned int version;
>  	static unsigned int top_index[256];
> -	const unsigned hashsz = the_hash_algo->rawsz;
> +	unsigned hashsz;
> +	const char *hash_name = NULL;
> +	int hash_algo;
> +	const struct option show_index_options[] = {
> +		OPT_STRING(0, "hash", &hash_name, N_("hash"),
> +			   N_("specify the hash algorithm to use")),

init-db has an entry identical to this except for the second token
given to the macro is "object-format" instead of "hash".  Both may
want to change what's inside N_() to "hash algorithm".

> +		OPT_END()
> +	};
> +
> +	argc = parse_options(argc, argv, prefix, show_index_options, show_index_usage, 0);
> +
> +	if (hash_name) {
> +		hash_algo = hash_algo_by_name(hash_name);
> +		if (hash_algo == GIT_HASH_UNKNOWN)
> +			die(_("Unknown hash algorithm"));
> +		repo_set_hash_algo(the_repository, hash_algo);
> +	}
> +
> +	hashsz = the_hash_algo->rawsz;
>  
> -	if (argc != 1)
> -		usage(show_index_usage);
>  	if (fread(top_index, 2 * 4, 1, stdin) != 1)
>  		die("unable to read header");
>  	if (top_index[0] == htonl(PACK_IDX_SIGNATURE)) {
> diff --git a/git.c b/git.c
> index 2e4efb4ff0..e53e8159a2 100644
> --- a/git.c
> +++ b/git.c
> @@ -573,7 +573,7 @@ static struct cmd_struct commands[] = {
>  	{ "shortlog", cmd_shortlog, RUN_SETUP_GENTLY | USE_PAGER },
>  	{ "show", cmd_show, RUN_SETUP },
>  	{ "show-branch", cmd_show_branch, RUN_SETUP },
> -	{ "show-index", cmd_show_index },
> +	{ "show-index", cmd_show_index, RUN_SETUP_GENTLY },

Hmph, this is not necessary to support peeking an .idx file in
another repository that uses a different hash algorithm than ours
(we do need the --hash=<algo> override to tell that the algo is
different from what we read from our repository settings).  Is this
absolutely necessary?

Ah, I am misreading the patch.  We didn't even do setup but we now
optionally do, in order to see if we are in a repository and what
object format it uses to give the default value to --hash=<algo>
when the argument is not given.  The need for RUN_SETUP_GENTLY
is understandable.

As we do not take any path argument on the command line, the other
side effect of setup_git_directory() that takes us up to the top
level of the working tree does not hurt us, either, so this is a
good change, I think.

Thanks.



>  	{ "show-ref", cmd_show_ref, RUN_SETUP },
>  	{ "sparse-checkout", cmd_sparse_checkout, RUN_SETUP | NEED_WORK_TREE },
>  	{ "stage", cmd_add, RUN_SETUP | NEED_WORK_TREE },

  reply	other threads:[~2020-05-18 16:20 UTC|newest]

Thread overview: 175+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13  0:53 [PATCH 00/44] SHA-256 part 2/3: protocol functionality brian m. carlson
2020-05-13  0:53 ` [PATCH 01/44] t1050: match object ID paths in a hash-insensitive way brian m. carlson
2020-05-13  0:53 ` [PATCH 02/44] Documentation: document v1 protocol object-format capability brian m. carlson
2020-05-13 19:28   ` Martin Ågren
2020-05-14  1:12     ` Junio C Hamano
2020-05-15 23:22       ` brian m. carlson
2020-05-16  0:02         ` Junio C Hamano
2020-05-13  0:53 ` [PATCH 03/44] connect: have ref processing code take struct packet_reader brian m. carlson
2020-05-13 19:30   ` Martin Ågren
2020-05-13  0:53 ` [PATCH 04/44] wrapper: add function to compare strings with different NUL termination brian m. carlson
2020-05-13 19:32   ` Martin Ågren
2020-05-13  0:53 ` [PATCH 05/44] remote: advertise the object-format capability on the server side brian m. carlson
2020-05-13  0:53 ` [PATCH 06/44] connect: add function to parse multiple v1 capability values brian m. carlson
2020-05-13  0:53 ` [PATCH 07/44] connect: add function to fetch value of a v2 server capability brian m. carlson
2020-05-13 19:37   ` Martin Ågren
2020-05-13  0:53 ` [PATCH 08/44] pkt-line: add a member for hash algorithm brian m. carlson
2020-05-13  0:53 ` [PATCH 09/44] transport: add a hash algorithm member brian m. carlson
2020-05-13  0:53 ` [PATCH 10/44] connect: add function to detect supported v1 hash functions brian m. carlson
2020-05-13 19:39   ` Martin Ågren
2020-05-13 22:49     ` brian m. carlson
2020-05-13  0:53 ` [PATCH 11/44] send-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-13 19:41   ` Martin Ågren
2020-05-13 22:52     ` brian m. carlson
2020-05-13  0:53 ` [PATCH 12/44] connect: make parse_feature_value extern brian m. carlson
2020-05-13 19:48   ` Martin Ågren
2020-05-13  0:53 ` [PATCH 13/44] fetch-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-13  0:53 ` [PATCH 14/44] connect: detect algorithm when fetching refs brian m. carlson
2020-05-16 10:40   ` Martin Ågren
2020-05-16 19:59     ` brian m. carlson
2020-05-13  0:53 ` [PATCH 15/44] builtin/receive-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-16 10:41   ` Martin Ågren
2020-05-13  0:53 ` [PATCH 16/44] docs: update remote helper docs for object-format extensions brian m. carlson
2020-05-13  0:53 ` [PATCH 17/44] transport-helper: implement " brian m. carlson
2020-05-13  0:53 ` [PATCH 18/44] remote-curl: " brian m. carlson
2020-05-13  0:53 ` [PATCH 19/44] builtin/clone: initialize hash algorithm properly brian m. carlson
2020-05-16 10:48   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 20/44] t5562: pass object-format in synthesized test data brian m. carlson
2020-05-16 10:55   ` Martin Ågren
2020-05-16 19:50     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 21/44] t5704: send object-format capability with SHA-256 brian m. carlson
2020-05-16 11:02   ` Martin Ågren
2020-05-16 19:14     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 22/44] fetch-pack: parse and advertise the object-format capability brian m. carlson
2020-05-16 11:03   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 23/44] setup: set the_repository's hash algo when checking format brian m. carlson
2020-05-16 11:03   ` Martin Ågren
2020-05-16 19:29     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 24/44] t3200: mark assertion with SHA1 prerequisite brian m. carlson
2020-05-16 11:04   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 25/44] packfile: compute and use the index CRC offset brian m. carlson
2020-05-16 11:12   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 26/44] t5302: modernize test formatting brian m. carlson
2020-05-13  0:54 ` [PATCH 27/44] builtin/show-index: provide options to determine hash algo brian m. carlson
2020-05-18 16:20   ` Junio C Hamano [this message]
2020-05-19  0:31     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 28/44] t1302: expect repo format version 1 for SHA-256 brian m. carlson
2020-05-13  0:54 ` [PATCH 29/44] Documentation/technical: document object-format for protocol v2 brian m. carlson
2020-05-13  0:54 ` [PATCH 30/44] connect: pass full packet reader when parsing v2 refs brian m. carlson
2020-05-16 11:13   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 31/44] connect: parse v2 refs with correct hash algorithm brian m. carlson
2020-05-16 11:14   ` Martin Ågren
2020-05-17 22:37     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 32/44] serve: advertise object-format capability for protocol v2 brian m. carlson
2020-05-16 11:15   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 33/44] t5500: make hash independent brian m. carlson
2020-05-13  0:54 ` [PATCH 34/44] builtin/ls-remote: initialize repository based on fetch brian m. carlson
2020-05-16 11:16   ` Martin Ågren
2020-05-16 20:28     ` brian m. carlson
2020-05-13  0:54 ` [PATCH 35/44] remote-curl: detect algorithm for dumb HTTP by size brian m. carlson
2020-05-16 11:17   ` Martin Ågren
2020-05-13  0:54 ` [PATCH 36/44] builtin/index-pack: add option to specify hash algorithm brian m. carlson
2020-05-16 11:18   ` Martin Ågren
2020-05-16 20:47     ` brian m. carlson
2020-05-17 18:16       ` Martin Ågren
2020-05-17 20:52         ` brian m. carlson
2020-05-13  0:54 ` [PATCH 37/44] t1050: pass algorithm to index-pack when outside repo brian m. carlson
2020-05-13  0:54 ` [PATCH 38/44] remote-curl: avoid truncating refs with ls-remote brian m. carlson
2020-05-13  0:54 ` [PATCH 39/44] t/helper: initialize the repository for test-sha1-array brian m. carlson
2020-05-13  0:54 ` [PATCH 40/44] t5702: offer an object-format capability in the test brian m. carlson
2020-05-13  0:54 ` [PATCH 41/44] t5703: use object-format serve option brian m. carlson
2020-05-13  0:54 ` [PATCH 42/44] t5300: pass --object-format to git index-pack brian m. carlson
2020-05-13  0:54 ` [PATCH 43/44] bundle: detect hash algorithm when reading refs brian m. carlson
2020-05-13  0:54 ` [PATCH 44/44] remote-testgit: adapt for object-format brian m. carlson
2020-05-25 19:58 ` [PATCH v2 00/44] SHA-256 part 2/3: protocol functionality brian m. carlson
2020-05-25 19:58   ` [PATCH v2 01/44] t1050: match object ID paths in a hash-insensitive way brian m. carlson
2020-05-25 19:58   ` [PATCH v2 02/44] Documentation: document v1 protocol object-format capability brian m. carlson
2020-05-25 19:58   ` [PATCH v2 03/44] connect: have ref processing code take struct packet_reader brian m. carlson
2020-05-25 19:58   ` [PATCH v2 04/44] wrapper: add function to compare strings with different NUL termination brian m. carlson
2020-05-25 19:58   ` [PATCH v2 05/44] remote: advertise the object-format capability on the server side brian m. carlson
2020-05-25 19:58   ` [PATCH v2 06/44] connect: add function to parse multiple v1 capability values brian m. carlson
2020-05-25 19:58   ` [PATCH v2 07/44] connect: add function to fetch value of a v2 server capability brian m. carlson
2020-05-25 19:58   ` [PATCH v2 08/44] pkt-line: add a member for hash algorithm brian m. carlson
2020-05-25 19:58   ` [PATCH v2 09/44] transport: add a hash algorithm member brian m. carlson
2020-05-25 19:58   ` [PATCH v2 10/44] connect: add function to detect supported v1 hash functions brian m. carlson
2020-05-25 19:58   ` [PATCH v2 11/44] send-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-25 19:58   ` [PATCH v2 12/44] connect: make parse_feature_value extern brian m. carlson
2020-05-25 19:58   ` [PATCH v2 13/44] fetch-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-25 19:59   ` [PATCH v2 14/44] connect: detect algorithm when fetching refs brian m. carlson
2020-05-25 19:59   ` [PATCH v2 15/44] builtin/receive-pack: detect when the server doesn't support our hash brian m. carlson
2020-05-25 19:59   ` [PATCH v2 16/44] docs: update remote helper docs for object-format extensions brian m. carlson
2020-05-25 19:59   ` [PATCH v2 17/44] transport-helper: implement " brian m. carlson
2020-05-25 19:59   ` [PATCH v2 18/44] remote-curl: " brian m. carlson
2020-05-25 19:59   ` [PATCH v2 19/44] builtin/clone: initialize hash algorithm properly brian m. carlson
2020-05-25 19:59   ` [PATCH v2 20/44] t5562: pass object-format in synthesized test data brian m. carlson
2020-05-25 19:59   ` [PATCH v2 21/44] fetch-pack: parse and advertise the object-format capability brian m. carlson
2020-05-25 19:59   ` [PATCH v2 22/44] setup: set the_repository's hash algo when checking format brian m. carlson
2020-05-25 19:59   ` [PATCH v2 23/44] t3200: mark assertion with SHA1 prerequisite brian m. carlson
2020-05-25 19:59   ` [PATCH v2 24/44] packfile: compute and use the index CRC offset brian m. carlson
2020-05-25 19:59   ` [PATCH v2 25/44] t5302: modernize test formatting brian m. carlson
2020-05-25 19:59   ` [PATCH v2 26/44] builtin/show-index: provide options to determine hash algo brian m. carlson
2020-05-25 19:59   ` [PATCH v2 27/44] t1302: expect repo format version 1 for SHA-256 brian m. carlson
2020-05-25 19:59   ` [PATCH v2 28/44] Documentation/technical: document object-format for protocol v2 brian m. carlson
2020-05-25 19:59   ` [PATCH v2 29/44] connect: pass full packet reader when parsing v2 refs brian m. carlson
2020-05-25 19:59   ` [PATCH v2 30/44] connect: parse v2 refs with correct hash algorithm brian m. carlson
2020-05-25 19:59   ` [PATCH v2 31/44] serve: advertise object-format capability for protocol v2 brian m. carlson
2020-05-25 19:59   ` [PATCH v2 32/44] t5500: make hash independent brian m. carlson
2020-05-25 19:59   ` [PATCH v2 33/44] builtin/ls-remote: initialize repository based on fetch brian m. carlson
2020-05-25 19:59   ` [PATCH v2 34/44] remote-curl: detect algorithm for dumb HTTP by size brian m. carlson
2020-05-25 19:59   ` [PATCH v2 35/44] builtin/index-pack: add option to specify hash algorithm brian m. carlson
2020-05-25 19:59   ` [PATCH v2 36/44] t1050: pass algorithm to index-pack when outside repo brian m. carlson
2020-05-25 19:59   ` [PATCH v2 37/44] remote-curl: avoid truncating refs with ls-remote brian m. carlson
2020-05-25 19:59   ` [PATCH v2 38/44] t/helper: initialize the repository for test-sha1-array brian m. carlson
2020-05-25 19:59   ` [PATCH v2 39/44] t5702: offer an object-format capability in the test brian m. carlson
2020-05-25 19:59   ` [PATCH v2 40/44] t5703: use object-format serve option brian m. carlson
2020-05-25 19:59   ` [PATCH v2 41/44] t5704: send object-format capability with SHA-256 brian m. carlson
2020-05-25 19:59   ` [PATCH v2 42/44] t5300: pass --object-format to git index-pack brian m. carlson
2020-05-25 19:59   ` [PATCH v2 43/44] bundle: detect hash algorithm when reading refs brian m. carlson
2020-05-25 19:59   ` [PATCH v2 44/44] remote-testgit: adapt for object-format brian m. carlson
2020-06-19 17:55 ` [PATCH v3 00/44] SHA-256 part 2/3: protocol functionality brian m. carlson
2020-06-19 17:55   ` [PATCH v3 01/44] t1050: match object ID paths in a hash-insensitive way brian m. carlson
2020-06-19 17:55   ` [PATCH v3 02/44] Documentation: document v1 protocol object-format capability brian m. carlson
2020-06-19 17:55   ` [PATCH v3 03/44] connect: have ref processing code take struct packet_reader brian m. carlson
2020-06-19 17:55   ` [PATCH v3 04/44] wrapper: add function to compare strings with different NUL termination brian m. carlson
2020-06-19 17:55   ` [PATCH v3 05/44] remote: advertise the object-format capability on the server side brian m. carlson
2020-06-19 17:55   ` [PATCH v3 06/44] connect: add function to parse multiple v1 capability values brian m. carlson
2020-06-19 17:55   ` [PATCH v3 07/44] connect: add function to fetch value of a v2 server capability brian m. carlson
2020-06-19 17:55   ` [PATCH v3 08/44] pkt-line: add a member for hash algorithm brian m. carlson
2020-06-19 17:55   ` [PATCH v3 09/44] transport: add a hash algorithm member brian m. carlson
2020-06-19 17:55   ` [PATCH v3 10/44] connect: add function to detect supported v1 hash functions brian m. carlson
2020-06-19 17:55   ` [PATCH v3 11/44] send-pack: detect when the server doesn't support our hash brian m. carlson
2020-06-19 17:55   ` [PATCH v3 12/44] connect: make parse_feature_value extern brian m. carlson
2020-06-19 17:55   ` [PATCH v3 13/44] fetch-pack: detect when the server doesn't support our hash brian m. carlson
2020-06-19 17:55   ` [PATCH v3 14/44] connect: detect algorithm when fetching refs brian m. carlson
2020-06-19 17:55   ` [PATCH v3 15/44] builtin/receive-pack: detect when the server doesn't support our hash brian m. carlson
2020-06-19 17:55   ` [PATCH v3 16/44] docs: update remote helper docs for object-format extensions brian m. carlson
2020-06-19 17:55   ` [PATCH v3 17/44] transport-helper: implement " brian m. carlson
2020-06-19 17:55   ` [PATCH v3 18/44] remote-curl: " brian m. carlson
2020-06-19 17:55   ` [PATCH v3 19/44] builtin/clone: initialize hash algorithm properly brian m. carlson
2020-06-19 17:55   ` [PATCH v3 20/44] t5562: pass object-format in synthesized test data brian m. carlson
2020-06-19 17:55   ` [PATCH v3 21/44] fetch-pack: parse and advertise the object-format capability brian m. carlson
2020-06-19 17:55   ` [PATCH v3 22/44] setup: set the_repository's hash algo when checking format brian m. carlson
2020-06-19 17:55   ` [PATCH v3 23/44] t3200: mark assertion with SHA1 prerequisite brian m. carlson
2020-06-19 17:55   ` [PATCH v3 24/44] packfile: compute and use the index CRC offset brian m. carlson
2020-06-19 17:55   ` [PATCH v3 25/44] t5302: modernize test formatting brian m. carlson
2020-06-19 17:55   ` [PATCH v3 26/44] builtin/show-index: provide options to determine hash algo brian m. carlson
2020-06-19 17:55   ` [PATCH v3 27/44] t1302: expect repo format version 1 for SHA-256 brian m. carlson
2020-06-19 17:55   ` [PATCH v3 28/44] Documentation/technical: document object-format for protocol v2 brian m. carlson
2020-06-19 17:55   ` [PATCH v3 29/44] connect: pass full packet reader when parsing v2 refs brian m. carlson
2020-06-19 17:55   ` [PATCH v3 30/44] connect: parse v2 refs with correct hash algorithm brian m. carlson
2020-06-19 17:55   ` [PATCH v3 31/44] serve: advertise object-format capability for protocol v2 brian m. carlson
2020-06-19 17:55   ` [PATCH v3 32/44] t5500: make hash independent brian m. carlson
2020-06-19 17:55   ` [PATCH v3 33/44] builtin/ls-remote: initialize repository based on fetch brian m. carlson
2020-06-19 17:55   ` [PATCH v3 34/44] remote-curl: detect algorithm for dumb HTTP by size brian m. carlson
2020-06-19 17:55   ` [PATCH v3 35/44] builtin/index-pack: add option to specify hash algorithm brian m. carlson
2020-06-19 17:55   ` [PATCH v3 36/44] t1050: pass algorithm to index-pack when outside repo brian m. carlson
2020-06-19 17:55   ` [PATCH v3 37/44] remote-curl: avoid truncating refs with ls-remote brian m. carlson
2020-06-19 17:55   ` [PATCH v3 38/44] t/helper: initialize the repository for test-sha1-array brian m. carlson
2020-06-19 17:55   ` [PATCH v3 39/44] t5702: offer an object-format capability in the test brian m. carlson
2020-06-19 17:55   ` [PATCH v3 40/44] t5703: use object-format serve option brian m. carlson
2020-06-19 17:55   ` [PATCH v3 41/44] t5704: send object-format capability with SHA-256 brian m. carlson
2020-06-19 17:55   ` [PATCH v3 42/44] t5300: pass --object-format to git index-pack brian m. carlson
2020-06-19 17:56   ` [PATCH v3 43/44] bundle: detect hash algorithm when reading refs brian m. carlson
2020-06-19 17:56   ` [PATCH v3 44/44] remote-testgit: adapt for object-format brian m. carlson
2020-06-19 21:09   ` [PATCH v3 00/44] SHA-256 part 2/3: protocol functionality Junio C Hamano
2020-06-20  1:33     ` brian m. carlson

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