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From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH v2 3/7] fetch: avoid reading submodule config until needed
Date: Wed, 12 Aug 2020 10:34:35 -0700	[thread overview]
Message-ID: <xmqqo8nf7opg.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <8b4a522a13089ea144e922280f1c71a4ec3afa1f.1597184949.git.jonathantanmy@google.com> (Jonathan Tan's message of "Tue, 11 Aug 2020 15:52:18 -0700")

Jonathan Tan <jonathantanmy@google.com> writes:

> Teach "git fetch" to avoid reading the submodule config until necessary.
> This allows users to avoid the lazy-fetching of this potentially missing
> config file by specifying the --recurse-submodules=no command line
> option.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  builtin/fetch.c    | 10 ++++++++--
>  submodule-config.c |  5 +++--
>  2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index a5498646bf..29db219c68 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -1786,12 +1786,18 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
>  		free(anon);
>  	}
>  
> -	fetch_config_from_gitmodules(&submodule_fetch_jobs_config,
> -				     &recurse_submodules);
>  	git_config(git_fetch_config, NULL);
>  
>  	argc = parse_options(argc, argv, prefix,
>  			     builtin_fetch_options, builtin_fetch_usage, 0);
> +	if (recurse_submodules != RECURSE_SUBMODULES_OFF) {
> +		int *sfjc = submodule_fetch_jobs_config == -1
> +			    ? &submodule_fetch_jobs_config : NULL;
> +		int *rs = recurse_submodules == RECURSE_SUBMODULES_DEFAULT
> +			  ? &recurse_submodules : NULL;
> +
> +		fetch_config_from_gitmodules(sfjc, rs);
> +	}

Hmph.  Instead of calling fetch_config_from... upfront, first
reading the fetch configuration and also command line options to see
if we are told to recurse, and only enter the new "if()" statement
does make sense---we'll avoid calling fetch_config_from... when we
are told not to recurse into submodules.

But it is not quite clear why the two parameters to the function can
now be conditional, and what benefit we gain by doing so, in the
body of the new "if()" statement.  Don't you need to explain to your
future peer developers what is going on here in the log message?

>  	if (deepen_relative) {
>  		if (deepen_relative < 0)
> diff --git a/submodule-config.c b/submodule-config.c
> index e175dfbc38..8d65273ed2 100644
> --- a/submodule-config.c
> +++ b/submodule-config.c
> @@ -776,10 +776,11 @@ struct fetch_config {
>  static int gitmodules_fetch_config(const char *var, const char *value, void *cb)
>  {
>  	struct fetch_config *config = cb;
> -	if (!strcmp(var, "submodule.fetchjobs")) {
> +	if (!strcmp(var, "submodule.fetchjobs") && config->max_children) {
>  		*(config->max_children) = parse_submodule_fetchjobs(var, value);
>  		return 0;

Because the new "if()" statement in cmd_fetch can pass NULL to
either of the two parameters to fetch_config_from_gitmodules(), it
now becomes possible for this function to get an instance of "struct
fetch_config" with .max_children field set to NULL.

The above justifies why assignment to *(config->max_children) must
be skipped when .max_children is NULL, but it does not justify the
new code, where .max_children==NULL does not stop the if/else if/
cascade.

	if (!strcmp(var, "submodule.fetchjobs")) {
		if (config->max_children)
			*(config->max_children) = parse...
		return 0;
	}

Why sfjc or rs is allowed to be NULL in certain cases, and why doing
so is a good idea, should be explained nevertheless, though.

> -	} else if (!strcmp(var, "fetch.recursesubmodules")) {
> +	} else if (!strcmp(var, "fetch.recursesubmodules") &&
> +		   config->recurse_submodules) {
>  		*(config->recurse_submodules) = parse_fetch_recurse_submodules_arg(var, value);
>  		return 0;

Likewise.

Thanks.


  reply	other threads:[~2020-08-12 17:35 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-24 22:38 [RFC PATCH] Modify fetch-pack to no longer die on error? Jonathan Tan
2020-07-24 23:07 ` Junio C Hamano
2020-07-24 23:11 ` Junio C Hamano
2020-07-25 21:41   ` Jeff King
2020-07-25 23:01     ` Junio C Hamano
2020-07-27 17:11       ` Jeff King
2020-07-28 19:23       ` Jonathan Tan
2020-07-28 20:08         ` Jeff King
2020-07-29 18:53           ` Jonathan Tan
2020-07-29 19:29             ` Jeff King
2020-07-29 19:02           ` Junio C Hamano
2020-07-29 22:55             ` Jonathan Tan
2020-08-05  1:20 ` [RFC PATCH 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip Jonathan Tan
2020-08-05 19:53     ` Junio C Hamano
2020-08-07 20:53       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 2/7] fetch-pack: allow NULL negotiator->known_common Jonathan Tan
2020-08-05 20:08     ` Junio C Hamano
2020-08-05 22:11       ` Junio C Hamano
2020-08-07 20:59         ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 3/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 4/7] fetch: --stdin Jonathan Tan
2020-08-05 20:33     ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-07 21:58         ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 5/7] fetch: submodule config Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 6/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 7/7] promisor-remote: use subprocess to fetch Jonathan Tan
2020-08-11 22:52 ` [PATCH v2 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 1/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-12 12:55     ` Derrick Stolee
2020-08-12 16:44       ` Junio C Hamano
2020-08-12 17:29         ` Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-12 17:34     ` Junio C Hamano [this message]
2020-08-11 22:52   ` [PATCH v2 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-12 18:06     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-12 18:25     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-12 18:28     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-12 12:51   ` [PATCH v2 0/7] Lazy fetch with subprocess Derrick Stolee
2020-08-18  4:01 ` [PATCH v3 " Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 1/7] negotiator/noop: add noop fetch negotiator Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-18 19:56   ` [PATCH v3 0/7] Lazy fetch with subprocess Junio C Hamano
2020-08-18 22:32     ` Junio C Hamano
2020-08-18 23:36       ` [PATCH] fixup! promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18 23:57         ` Junio C Hamano

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