# [GSoC PATCH v2] backfill: auto-detect sparse-checkout from config 3 messages from 2026-04-04 to 2026-04-06. Participants: Trieu Huynh, Derrick Stolee, Junio C Hamano. Thread: https://gitlist.dev/t/65432 ## Trieu Huynh, 2026-04-04 11:15 Subject: [GSoC PATCH v2] backfill: auto-detect sparse-checkout from config Message-ID: <20260404111557.17220-1-viking4@gmail.com> ``` From: Trieu Huynh Commit 85127bcdea ("backfill: assume --sparse when sparse-checkout is enabled") intended for 'git backfill' to consult the repository configuration when the user does not pass '--sparse' or '--no-sparse' on the command line. It added the sentinel check: if (ctx->sparse < 0) ctx->sparse = cfg->apply_sparse_checkout; However, the ctx->sparse field is initialized to 0 instead of -1, so this guard never triggers. Consequently, the repository config (core.sparseCheckout) is never checked, and the command always performs a full backfill even when sparse-checkout is enabled. Fix this by initializing ctx->sparse to -1, ensuring the existing fallback logic correctly reads the repository configuration when no explicit flags are provided. Add a test to verify that 'git backfill' automatically respects sparse-checkout settings when no flags are passed. Signed-off-by: Trieu Huynh --- v2: - Update commit message to explicitly point to addressing 85127bcdea. - The code change itself is unchanged. builtin/backfill.c | 2 +- t/t5620-backfill.sh | 15 +++++++++++++++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/builtin/backfill.c b/builtin/backfill.c index e80fc1b694..54acdfe290 100644 --- a/builtin/backfill.c +++ b/builtin/backfill.c @@ -120,7 +120,7 @@ int cmd_backfill(int argc, const char **argv, const char *prefix, struct reposit .repo = repo, .current_batch = OID_ARRAY_INIT, .min_batch_size = 50000, - .sparse = 0, + .sparse = -1, }; struct option options[] = { OPT_UNSIGNED(0, "min-batch-size", &ctx.min_batch_size, diff --git a/t/t5620-backfill.sh b/t/t5620-backfill.sh index 58c81556e7..bed4987124 100755 --- a/t/t5620-backfill.sh +++ b/t/t5620-backfill.sh @@ -119,6 +119,21 @@ test_expect_success 'backfill --sparse' ' test_line_count = 0 missing ' +test_expect_success 'backfill auto-detects sparse-checkout from config' ' + git clone --sparse --filter=blob:none \ + --single-branch --branch=main \ + "file://$(pwd)/srv.bare" backfill-auto-sparse && + + git -C backfill-auto-sparse rev-list --quiet --objects --missing=print HEAD >missing && + test_line_count = 44 missing && + + GIT_TRACE2_EVENT="$(pwd)/auto-sparse-trace" git \ + -C backfill-auto-sparse backfill && + + test_trace2_data promisor fetch_count 4 In-Reply-To: <20260404111557.17220-1-viking4@gmail.com> ``` On 4/4/26 7:15 AM, Trieu Huynh wrote: > From: Trieu Huynh > > Commit 85127bcdea ("backfill: assume --sparse when sparse-checkout is > enabled") intended for 'git backfill' to consult the repository > configuration when the user does not pass '--sparse' or > '--no-sparse' on the command line. It added the sentinel check: > > if (ctx->sparse < 0) > ctx->sparse = cfg->apply_sparse_checkout; > > However, the ctx->sparse field is initialized to 0 instead of -1, > so this guard never triggers. Consequently, the repository config > (core.sparseCheckout) is never checked, and the command always > performs a full backfill even when sparse-checkout is enabled. Thanks for adding this context. This patch LGTM. nit: it helps to reply to your previous version [1] so the history of your patch series shows up in a single thread. No need to fix it now because this version should be final. I'm a fan of using GitGitGadget to avoid making these kinds of mistakes, but you can use 'git send-email --in-reply-to=' [2] in the future. [1] https://lore.kernel.org/git/20260402191359.11304-1-viking4@gmail.com/ [2] https://git-scm.com/docs/git-send-email#Documentation/git-send-email.txt---in-reply-toidentifier Thanks, -Stolee ``` ## Junio C Hamano, 2026-04-06 16:27 Subject: Re: [GSoC PATCH v2] backfill: auto-detect sparse-checkout from config Message-ID: In-Reply-To: ``` Derrick Stolee writes: > On 4/4/26 7:15 AM, Trieu Huynh wrote: >> From: Trieu Huynh >> >> Commit 85127bcdea ("backfill: assume --sparse when sparse-checkout is >> enabled") intended for 'git backfill' to consult the repository >> configuration when the user does not pass '--sparse' or >> '--no-sparse' on the command line. It added the sentinel check: >> >> if (ctx->sparse < 0) >> ctx->sparse = cfg->apply_sparse_checkout; >> >> However, the ctx->sparse field is initialized to 0 instead of -1, >> so this guard never triggers. Consequently, the repository config >> (core.sparseCheckout) is never checked, and the command always >> performs a full backfill even when sparse-checkout is enabled. > > Thanks for adding this context. This patch LGTM. Yup, thanks, both of you. The original patch without this explanation may not be so obvious but after taking a look at what that commit did, it is very clear what went wrong. ```