Subject: Re: [PATCH v4 6/7] fetch: after refetch, encourage auto gc repacking

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 31 Mar 2022 17:22:52 +0200

On Mon, Mar 28 2022, Robert Coup via GitGitGadget wrote:

> From: Robert Coup <[email-masked]>
>
> After invoking `fetch --refetch`, the object db will likely contain many
> duplicate objects. If auto-maintenance is enabled, invoke it with
> appropriate settings to encourage repacking/consolidation.
>
> * gc.autoPackLimit: unless this is set to 0 (disabled), override the
>   value to 1 to force pack consolidation.
> * maintenance.incremental-repack.auto: unless this is set to 0, override
>   the value to -1 to force incremental repacking.
>
> Signed-off-by: Robert Coup <[email-masked]>
> ---
>  Documentation/fetch-options.txt |  3 ++-
>  builtin/fetch.c                 | 19 ++++++++++++++++++-
>  t/t5616-partial-clone.sh        | 29 +++++++++++++++++++++++++++++
>  3 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
> index d03fce5aae0..622bd84768b 100644
> --- a/Documentation/fetch-options.txt
> +++ b/Documentation/fetch-options.txt
> @@ -169,7 +169,8 @@ ifndef::git-pull[]
>  	associated objects that are already present locally, this option fetches
>  	all objects as a fresh clone would. Use this to reapply a partial clone
>  	filter from configuration or using `--filter=` when the filter
> -	definition has changed.
> +	definition has changed. Automatic post-fetch maintenance will perform
> +	object database pack consolidation to remove any duplicate objects.
>  endif::git-pull[]
>  
>  --refmap=<refspec>::
> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index e391a5dbc55..e3791f09ed5 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -2306,8 +2306,25 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
>  					     NULL);
>  	}
>  
> -	if (enable_auto_gc)
> +	if (enable_auto_gc) {
> +		if (refetch) {
> +			/*
> +			 * Hint auto-maintenance strongly to encourage repacking,
> +			 * but respect config settings disabling it.
> +			 */
> +			int opt_val;

nit: add a \n after this.

> +			if (git_config_get_int("gc.autopacklimit", &opt_val))
> +				opt_val = -1;
> +			if (opt_val != 0)

nit: don't compare against 0 or null,  just !opt_val

Isn't this whole thing also clearer as:

	int &forget;

        if (git_conf...(..., &forget))
		git_config_push_parameter("gc.autoPackLimit=1");

Maybe I haven't eyeballed this enough, but aren't you ignoring explicit
gc.autoPackLimit=0 configuration? Whereas what you seem to want is "set
this config unlress the user has it set", for which we only need to
check the git_config...(...) return value, no?

> +				git_config_push_parameter("gc.autoPackLimit=1");
> +
> +			if (git_config_get_int("maintenance.incremental-repack.auto", &opt_val))
> +				opt_val = -1;
> +			if (opt_val != 0)
> +				git_config_push_parameter("maintenance.incremental-repack.auto=-1");

hrm, do we really need to set both of these these days (not saying we
don't, just surprised). I.e. both gc.* an maintenance.* config.

*skims the code*

Urgh, yes? too_many_packs() seems to check gc.* only, but
incremental_repack_auto_condition() check this variable... :(

> +test_expect_success 'fetch --refetch triggers repacking' '
> +	GIT_TRACE2_CONFIG_PARAMS=gc.autoPackLimit,maintenance.incremental-repack.auto &&

Nit: Can we use GIT_CONFIG_KEY_* et al for this these days, or do we
still need this trace2 thingy?

> +	export GIT_TRACE2_CONFIG_PARAMS &&
> +