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From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, stolee@gmail.com
Subject: Re: [PATCH v3 0/7] Lazy fetch with subprocess
Date: Tue, 18 Aug 2020 12:56:22 -0700	[thread overview]
Message-ID: <xmqqimdfybh5.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <cover.1597722941.git.jonathantanmy@google.com> (Jonathan Tan's message of "Mon, 17 Aug 2020 21:01:30 -0700")

Jonathan Tan <jonathantanmy@google.com> writes:

> These patches are based on jc/no-update-fetch-head, once again.

FWIW, that topic no longer exists (it has been swallowed by
Derrick's maintenance topics).  As that topic is not near 'next'
yet, we might want to kick the patch out of it into a separate
jc/no-update-fetch-head topic again, base this series and also
maintenance topics on top of it.

> 2:  00ad7dd875 = 2:  9f277f1631 fetch: allow refspecs specified through stdin
> 3:  8b4a522a13 ! 3:  fda9f834f6 fetch: avoid reading submodule config until needed
>     @@ Metadata
>       ## Commit message ##
>          fetch: avoid reading submodule config until needed
>      
>     -    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.
>     +    In "fetch", there are two parameters submodule_fetch_jobs_config and
>     +    recurse_submodules that can be set in a variety of ways: through
>     +    .gitmodules, through .git/config, and through the command line.
>     +    Currently "fetch" handles this by first reading .gitmodules, then
>     +    reading .git/config (allowing it to overwrite existing values), then
>     +    reading the command line (allowing it to overwrite existing values).
>     +
>     +    Notice that we can avoid reading .gitmodules if .git/config and/or the
>     +    command line already provides us with what we need. In addition, if
>     +    recurse_submodules is found to be "no", we do not need the value of
>     +    submodule_fetch_jobs_config.
>     +
>     +    Avoiding reading .gitmodules is especially important when we use "git
>     +    fetch" to perform lazy fetches in a partial clone because the
>     +    .gitmodules file itself might need to be lazy fetched (and otherwise
>     +    causing an infinite loop).
>     +
>     +    In light of all this, avoid reading .gitmodules until necessary. When
>     +    reading it, we may only need one of the two parameters it provides, so
>     +    teach fetch_config_from_gitmodules() to support NULL arguments. With
>     +    this patch, users (including Git itself when invoking "git fetch" to
>     +    lazy-fetch) will be able to guarantee avoiding reading .gitmodules by
>     +    passing --recurse-submodules=no.

Quite sensible.

> 4:  77bc83e7f2 ! 4:  a5554cd27f fetch: only populate existing_refs if needed
>     @@ Metadata
>       ## Commit message ##
>          fetch: only populate existing_refs if needed
>      
>     -    When fetching tags, Git only writes tags that do not already exist in
>     -    the client repository. This necessitates an iteration over all the refs,
>     -    but fetch performs this iteration even if no tags are fetched.
>     +    In "fetch", get_ref_map() iterates over all refs to populate
>     +    "existing_refs" in order to populate peer_ref->old_oid in the returned
>     +    refmap, even if the refmap has no peer_ref set - which is the case when
>     +    only literal hashes (i.e. no refs by name) are fetched.

Much better---the previous round gave us a wrong impression that
the change is about the behaviour when fetching tags, but the
updated explanation makes it clear that the primary use case is to
avoid tag-following while directly fetching objects by names, not
via refs.

  parent reply	other threads:[~2020-08-18 19:56 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
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   ` Junio C Hamano [this message]
2020-08-18 22:32     ` [PATCH v3 0/7] Lazy fetch with subprocess 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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