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> On Sat, Mar 28, 2020 at 10:40:23AM -0400, Jeff King wrote:
>
>> So I guess the problem is not with shallow clones specifically, but they
>> lead us to not having fetched the commits pointed to by tags, which
>> leads to us trying to fault in those commits (and their trees) rather
>> than realizing that we weren't meant to have them. And the size of the
>> local repo balloons because you're fetching all those commits one by
>> one, and not getting the benefit of the deltas you would when you do a
>> single --filter=blob:none fetch.
>>
>> I guess we need something like this:
>
> The issue is actually with --single-branch, which is implied by --depth.
> But the fix is the same either way.
>
> Here it is with a commit message and test.
>
> -- >8 --
> Subject: [PATCH] clone: use "quick" lookup while following tags
>
> When cloning with --single-branch, we implement git-fetch's usual
> tag-following behavior, grabbing any tag objects that point to objects
> we have locally.
>
> When we're a partial clone, though, our has_object_file() check will
> actually lazy-fetch each tag. That not only defeats the purpose of
> --single-branch, but it does it incredibly slowly, potentially kicking
> off a new fetch for each tag. This is even worse for a shallow clone,
> which implies --single-branch, because even tags which are supersets of
> each other will be fetched individually.
>
> We can fix this by passing OBJECT_INFO_SKIP_FETCH_OBJECT to the call,
> which is what git-fetch does in this case.
>
> Likewise, let's include OBJECT_INFO_QUICK, as that's what git-fetch
> does. The rationale is discussed in 5827a03545 (fetch: use "quick"
> has_sha1_file for tag following, 2016-10-13), but here the tradeoff
> would apply even more so because clone is very unlikely to be racing
> with another process repacking our newly-created repository.
>
> This may provide a very small speedup even in the non-partial case case,
> as we'd avoid calling reprepare_packed_git() for each tag (though in
> practice, we'd only have a single packfile, so that reprepare should be
> quite cheap).
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> builtin/clone.c | 4 +++-
> t/t5616-partial-clone.sh | 8 ++++++++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/builtin/clone.c b/builtin/clone.c
> index d8b1f413aa..9da6459f1d 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -643,7 +643,9 @@ static void write_followtags(const struct ref *refs, const char *msg)
> continue;
> if (ends_with(ref->name, "^{}"))
> continue;
> - if (!has_object_file(&ref->old_oid))
> + if (!has_object_file_with_flags(&ref->old_oid,
> + OBJECT_INFO_QUICK |
> + OBJECT_INFO_SKIP_FETCH_OBJECT))
> continue;
> update_ref(msg, ref->name, &ref->old_oid, NULL, 0,
> UPDATE_REFS_DIE_ON_ERR);
> diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh
> index 77bb91e976..8f0d81a27e 100755
> --- a/t/t5616-partial-clone.sh
> +++ b/t/t5616-partial-clone.sh
> @@ -415,6 +415,14 @@ test_expect_success 'verify fetch downloads only one pack when updating refs' '
> test_line_count = 3 pack-list
> '
>
> +test_expect_success 'single-branch tag following respects partial clone' '
> + git clone --single-branch -b B --filter=blob:none \
> + "file://$(pwd)/srv.bare" single &&
> + git -C single rev-parse --verify refs/tags/B &&
> + git -C single rev-parse --verify refs/tags/A &&
> + test_must_fail git -C single rev-parse --verify refs/tags/C
> +'
> +
> . "$TEST_DIRECTORY"/lib-httpd.sh
> start_httpd
>
> --
> 2.26.0.408.gebd8a4413c