Subject: [PATCH] bundle-uri: refresh packed_git if unbundle succeed

From: "blanet via GitGitGadget" <[email-masked]>
Date: Wed, 15 May 2024 03:01:09 +0000

From: Xing Xin <[email-masked]>

When using the bundle-uri mechanism with a bundle list containing
multiple interrelated bundles, we encountered a bug where tips from
downloaded bundles were not being discovered, resulting in rather slow
clones. This was particularly problematic when employing the heuristic
`creationTokens`.

And this is easy to reproduce. Suppose we have a repository with a
single branch `main` pointing to commit `A`, firstly we create a base
bundle with

  git bundle create base.bundle main

Then let's add a new commit `B` on top of `A`, so that an incremental
bundle for `main` can be created with

  git bundle create incr.bundle A..main

Now we can generate a bundle list with the following content:

  [bundle]
      version = 1
      mode = all
      heuristic = creationToken

  [bundle "base"]
      uri = base.bundle
      creationToken = 1

  [bundle "incr"]
      uri = incr.bundle
      creationToken = 2

A fresh clone with the bundle list above would give the expected
`refs/bundles/main` pointing at `B` in new repository, in other words we
already had everything locally from the bundles, but git would still
download everything from server as if we got nothing.

So why the `refs/bundles/main` is not discovered? After some digging I
found that:

1. when unbundling a downloaded bundle, a `verify_bundle` is called to
   check its prerequisites if any. The verify procedure would find oids
   so `packed_git` is initialized.

2. after unbundled all bundles, we would enter `do_fetch_pack_v2`,
   during which `mark_complete_and_common_ref` and `mark_tips` would
   find oids with `OBJECT_INFO_QUICK` flag set, so no new packs would be
   enlisted if `packed_git` has already initialized in 1.

Back to the example above, when unbunding `incr.bundle`, `base.pack` is
enlisted to `packed_git` bacause of the prerequisites to verify. Then we
can not find `B` for negotiation at a latter time bacause `B` exists in
`incr.pack` which is not enlisted in `packed_git`.

This commit fixes this by adding a `reprepare_packed_git` call for every
successfully unbundled bundle, which ensures to enlist all generated
packs from bundle uri. And a set of negotiation related tests are added.

Signed-off-by: Xing Xin <[email-masked]>
---
    bundle-uri: refresh packed_git if unbundle succeed

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1730%2Fblanet%2Fxx%2Fbundle-uri-bug-using-bundle-list-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1730/blanet/xx/bundle-uri-bug-using-bundle-list-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1730

 bundle-uri.c                |   3 +
 t/t5558-clone-bundle-uri.sh | 129 ++++++++++++++++++++++++++++++++++++
 2 files changed, 132 insertions(+)

diff --git a/bundle-uri.c b/bundle-uri.c
index ca32050a78f..2b9d36cfd8e 100644
--- a/bundle-uri.c
+++ b/bundle-uri.c
@@ -7,6 +7,7 @@
 #include "refs.h"
 #include "run-command.h"
 #include "hashmap.h"
+#include "packfile.h"
 #include "pkt-line.h"
 #include "config.h"
 #include "remote.h"
@@ -376,6 +377,8 @@ static int unbundle_from_file(struct repository *r, const char *file)
 			       VERIFY_BUNDLE_QUIET)))
 		return 1;
 
+	reprepare_packed_git(r);
+
 	/*
 	 * Convert all refs/heads/ from the bundle into refs/bundles/
 	 * in the local repository.
diff --git a/t/t5558-clone-bundle-uri.sh b/t/t5558-clone-bundle-uri.sh
index 1ca5f745e73..a5b04d6f187 100755
--- a/t/t5558-clone-bundle-uri.sh
+++ b/t/t5558-clone-bundle-uri.sh
@@ -20,7 +20,10 @@ test_expect_success 'fail to clone from non-bundle file' '
 test_expect_success 'create bundle' '
 	git init clone-from &&
 	git -C clone-from checkout -b topic &&
+
 	test_commit -C clone-from A &&
+	git -C clone-from bundle create A.bundle topic &&
+
 	test_commit -C clone-from B &&
 	git -C clone-from bundle create B.bundle topic
 '
@@ -259,6 +262,132 @@ test_expect_success 'clone bundle list (file, any mode, all failures)' '
 	! grep "refs/bundles/" refs
 '
 
+#########################################################################
+# Clone negotiation related tests begin here
+
+test_expect_success 'negotiation: bundle with part of wanted commits' '
+	test_when_finished rm -rf trace*.txt &&
+	GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+	git clone --no-local --bundle-uri="clone-from/A.bundle" \
+		clone-from nego-bundle-part &&
+	git -C nego-bundle-part for-each-ref --format="%(refname)" >refs &&
+	grep "refs/bundles/" refs >actual &&
+	cat >expect <<-\EOF &&
+	refs/bundles/topic
+	EOF
+	test_cmp expect actual &&
+	# Ensure that refs/bundles/topic are sent as "have".
+	grep "clone> have $(git -C clone-from rev-parse A)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle with all wanted commits' '
+	test_when_finished rm -rf trace*.txt &&
+	GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+	git clone --no-local --single-branch --branch=topic --no-tags \
+		--bundle-uri="clone-from/B.bundle" \
+		clone-from nego-bundle-all &&
+	git -C nego-bundle-all for-each-ref --format="%(refname)" >refs &&
+	grep "refs/bundles/" refs >actual &&
+	cat >expect <<-\EOF &&
+	refs/bundles/topic
+	EOF
+	test_cmp expect actual &&
+	# We already have all needed commits so no "want" needed.
+	! grep "clone> want " trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list (no heuristic)' '
+	test_when_finished rm -f trace*.txt &&
+	cat >bundle-list <<-EOF &&
+	[bundle]
+		version = 1
+		mode = all
+
+	[bundle "bundle-1"]
+		uri = file://$(pwd)/clone-from/bundle-1.bundle
+
+	[bundle "bundle-2"]
+		uri = file://$(pwd)/clone-from/bundle-2.bundle
+	EOF
+
+	GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+	git clone --no-local --bundle-uri="file://$(pwd)/bundle-list" \
+		clone-from nego-bundle-list-no-heuristic &&
+
+	git -C nego-bundle-list-no-heuristic for-each-ref --format="%(refname)" >refs &&
+	grep "refs/bundles/" refs >actual &&
+	cat >expect <<-\EOF &&
+	refs/bundles/base
+	refs/bundles/left
+	EOF
+	test_cmp expect actual &&
+	grep "clone> have $(git -C nego-bundle-list-no-heuristic rev-parse refs/bundles/left)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list (creationToken)' '
+	test_when_finished rm -f trace*.txt &&
+	cat >bundle-list <<-EOF &&
+	[bundle]
+		version = 1
+		mode = all
+		heuristic = creationToken
+
+	[bundle "bundle-1"]
+		uri = file://$(pwd)/clone-from/bundle-1.bundle
+		creationToken = 1
+
+	[bundle "bundle-2"]
+		uri = file://$(pwd)/clone-from/bundle-2.bundle
+		creationToken = 2
+	EOF
+
+	GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+	git clone --no-local --bundle-uri="file://$(pwd)/bundle-list" \
+		clone-from nego-bundle-list-heuristic &&
+
+	git -C nego-bundle-list-heuristic for-each-ref --format="%(refname)" >refs &&
+	grep "refs/bundles/" refs >actual &&
+	cat >expect <<-\EOF &&
+	refs/bundles/base
+	refs/bundles/left
+	EOF
+	test_cmp expect actual &&
+	grep "clone> have $(git -C nego-bundle-list-heuristic rev-parse refs/bundles/left)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list with all wanted commits' '
+	test_when_finished rm -f trace*.txt &&
+	cat >bundle-list <<-EOF &&
+	[bundle]
+		version = 1
+		mode = all
+		heuristic = creationToken
+
+	[bundle "bundle-1"]
+		uri = file://$(pwd)/clone-from/bundle-1.bundle
+		creationToken = 1
+
+	[bundle "bundle-2"]
+		uri = file://$(pwd)/clone-from/bundle-2.bundle
+		creationToken = 2
+	EOF
+
+	GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+	git clone --no-local --single-branch --branch=left --no-tags \
+		--bundle-uri="file://$(pwd)/bundle-list" \
+		clone-from nego-bundle-list-all &&
+
+	git -C nego-bundle-list-all for-each-ref --format="%(refname)" >refs &&
+	grep "refs/bundles/" refs >actual &&
+	cat >expect <<-\EOF &&
+	refs/bundles/base
+	refs/bundles/left
+	EOF
+	test_cmp expect actual &&
+	# We already have all needed commits so no "want" needed.
+	! grep "clone> want " trace-packet.txt
+'
+
 #########################################################################
 # HTTP tests begin here

base-commit: 83f1add914c6b4682de1e944ec0d1ac043d53d78
-- 
gitgitgadget