fetch-pack: support negotiation tip whitelist

During negotiation, fetch-pack eventually reports as "have" lines all
commits reachable from all refs. Allow the user to restrict the commits
sent in this way by providing a whitelist of tips; only the tips
themselves and their ancestors will be sent.

Both globs and single objects are supported.

This feature is only supported for protocols that support connect or
stateless-connect (such as HTTP with protocol v2).

This will speed up negotiation when the repository has multiple
relatively independent branches (for example, when a repository
interacts with multiple repositories, such as with linux-next [1] and
torvalds/linux [2]), and the user knows which local branch is likely to
have commits in common with the upstream branch they are fetching.

[1] https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next/
[2] https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux/

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index e402aee..4e6d049 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -865,4 +865,82 @@ test_expect_success C_LOCALE_OUTPUT 'fetch compact output' '
 	test_cmp expect actual
 '
 
+setup_negotiation_tip () {
+	SERVER="$1"
+	URL="$2"
+	USE_PROTOCOL_V2="$3"
+
+	rm -rf "$SERVER" client trace &&
+	git init "$SERVER" &&
+	test_commit -C "$SERVER" alpha_1 &&
+	test_commit -C "$SERVER" alpha_2 &&
+	git -C "$SERVER" checkout --orphan beta &&
+	test_commit -C "$SERVER" beta_1 &&
+	test_commit -C "$SERVER" beta_2 &&
+
+	git clone "$URL" client &&
+
+	if test "$USE_PROTOCOL_V2" -eq 1
+	then
+		git -C "$SERVER" config protocol.version 2 &&
+		git -C client config protocol.version 2
+	fi &&
+
+	test_commit -C "$SERVER" beta_s &&
+	git -C "$SERVER" checkout master &&
+	test_commit -C "$SERVER" alpha_s &&
+	git -C "$SERVER" tag -d alpha_1 alpha_2 beta_1 beta_2
+}
+
+check_negotiation_tip () {
+	# Ensure that {alpha,beta}_1 are sent as "have", but not {alpha_beta}_2
+	ALPHA_1=$(git -C client rev-parse alpha_1) &&
+	grep "fetch> have $ALPHA_1" trace &&
+	BETA_1=$(git -C client rev-parse beta_1) &&
+	grep "fetch> have $BETA_1" trace &&
+	ALPHA_2=$(git -C client rev-parse alpha_2) &&
+	! grep "fetch> have $ALPHA_2" trace &&
+	BETA_2=$(git -C client rev-parse beta_2) &&
+	! grep "fetch> have $BETA_2" trace
+}
+
+test_expect_success '--negotiation-tip limits "have" lines sent' '
+	setup_negotiation_tip server server 0 &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--negotiation-tip=alpha_1 --negotiation-tip=beta_1 \
+		origin alpha_s beta_s &&
+	check_negotiation_tip
+'
+
+test_expect_success '--negotiation-tip understands globs' '
+	setup_negotiation_tip server server 0 &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--negotiation-tip=*_1 \
+		origin alpha_s beta_s &&
+	check_negotiation_tip
+'
+
+test_expect_success '--negotiation-tip understands abbreviated SHA-1' '
+	setup_negotiation_tip server server 0 &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--negotiation-tip=$(git -C client rev-parse --short alpha_1) \
+		--negotiation-tip=$(git -C client rev-parse --short beta_1) \
+		origin alpha_s beta_s &&
+	check_negotiation_tip
+'
+
+. "$TEST_DIRECTORY"/lib-httpd.sh
+start_httpd
+
+test_expect_success '--negotiation-tip limits "have" lines sent with HTTP protocol v2' '
+	setup_negotiation_tip "$HTTPD_DOCUMENT_ROOT_PATH/server" \
+		"$HTTPD_URL/smart/server" 1 &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--negotiation-tip=alpha_1 --negotiation-tip=beta_1 \
+		origin alpha_s beta_s &&
+	check_negotiation_tip
+'
+
+stop_httpd
+
 test_done