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From: Jonathan Tan <jonathantanmy@google.com>
To: git@vger.kernel.org
Cc: peff@peff.net, felipe.contreras@gmail.com, gitster@pobox.com,
	avarab@gmail.com, Jonathan Tan <jonathantanmy@google.com>
Subject: [PATCH v2 1/3] ls-refs: report unborn targets of symrefs
Date: Tue, 15 Dec 2020 18:07:56 -0800	[thread overview]
Message-ID: <7f5b50c7b284f2630fe5be6455cc5d3e03b1eb70.1608084282.git.jonathantanmy@google.com> (raw)
In-Reply-To: <cover.1608084282.git.jonathantanmy@google.com>

When cloning, we choose the default branch based on the remote HEAD.
But if there is no remote HEAD reported (which could happen if the
target of the remote HEAD is unborn), we'll fall back to using our local
init.defaultBranch. Traditionally this hasn't been a big deal, because
most repos used "master" as the default. But these days it is likely to
cause confusion if the server and client implementations choose
different values (e.g., if the remote started with "main", we may choose
"master" locally, create commits there, and then the user is surprised
when they push to "master" and not "main").

To solve this, the remote needs to communicate the target of the HEAD
symref, even if it is unborn, and "git clone" needs to use this
information.

Currently, symrefs that have unborn targets (such as in this case) are
not communicated by the protocol. Teach Git to advertise and support the
"unborn" feature in "ls-refs" (guarded by the lsrefs.unborn config).
This feature indicates that "ls-refs" supports the "unborn" argument;
when it is specified, "ls-refs" will send the HEAD symref with the name
of its unborn target.

This change is only for protocol v2. A similar change for protocol v0
would require independent protocol design (there being no analogous
position to signal support for "unborn") and client-side plumbing of the
data required, so the scope of this patch set is limited to protocol v2.

The client side will be updated to use this in a subsequent commit.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 Documentation/technical/protocol-v2.txt | 10 ++++-
 ls-refs.c                               | 54 +++++++++++++++++++++++--
 ls-refs.h                               |  1 +
 serve.c                                 |  2 +-
 4 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index e597b74da3..dfe03aa114 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -192,11 +192,19 @@ ls-refs takes in the following arguments:
 	When specified, only references having a prefix matching one of
 	the provided prefixes are displayed.
 
+If the 'unborn' feature is advertised the following argument can be
+included in the client's request.
+
+    unborn
+	The server may send symrefs pointing to unborn branches in the form
+	"unborn <refname> symref-target:<target>".
+
 The output of ls-refs is as follows:
 
     output = *ref
 	     flush-pkt
-    ref = PKT-LINE(obj-id SP refname *(SP ref-attribute) LF)
+    obj-id-or-unborn = (obj-id | "unborn")
+    ref = PKT-LINE(obj-id-or-unborn SP refname *(SP ref-attribute) LF)
     ref-attribute = (symref | peeled)
     symref = "symref-target:" symref-target
     peeled = "peeled:" obj-id
diff --git a/ls-refs.c b/ls-refs.c
index a1e0b473e4..fdb644b482 100644
--- a/ls-refs.c
+++ b/ls-refs.c
@@ -32,6 +32,8 @@ struct ls_refs_data {
 	unsigned peel;
 	unsigned symrefs;
 	struct strvec prefixes;
+	unsigned allow_unborn : 1;
+	unsigned unborn : 1;
 };
 
 static int send_ref(const char *refname, const struct object_id *oid,
@@ -47,7 +49,10 @@ static int send_ref(const char *refname, const struct object_id *oid,
 	if (!ref_match(&data->prefixes, refname_nons))
 		return 0;
 
-	strbuf_addf(&refline, "%s %s", oid_to_hex(oid), refname_nons);
+	if (oid)
+		strbuf_addf(&refline, "%s %s", oid_to_hex(oid), refname_nons);
+	else
+		strbuf_addf(&refline, "unborn %s", refname_nons);
 	if (data->symrefs && flag & REF_ISSYMREF) {
 		struct object_id unused;
 		const char *symref_target = resolve_ref_unsafe(refname, 0,
@@ -74,8 +79,28 @@ static int send_ref(const char *refname, const struct object_id *oid,
 	return 0;
 }
 
-static int ls_refs_config(const char *var, const char *value, void *data)
+static void send_possibly_unborn_head(struct ls_refs_data *data)
 {
+	struct strbuf namespaced = STRBUF_INIT;
+	struct object_id oid;
+	int flag;
+	int null_oid;
+
+	strbuf_addf(&namespaced, "%sHEAD", get_git_namespace());
+	resolve_ref_unsafe(namespaced.buf, 0, &oid, &flag);
+	null_oid = is_null_oid(&oid);
+	if (!null_oid || (data->symrefs && (flag & REF_ISSYMREF)))
+		send_ref(namespaced.buf, null_oid ? NULL : &oid, flag, data);
+	strbuf_release(&namespaced);
+}
+
+static int ls_refs_config(const char *var, const char *value, void *cb_data)
+{
+	struct ls_refs_data *data = cb_data;
+
+	if (!strcmp("lsrefs.unborn", var))
+		data->allow_unborn = !strcmp(value, "allow") ||
+			!strcmp(value, "advertise");
 	/*
 	 * We only serve fetches over v2 for now, so respect only "uploadpack"
 	 * config. This may need to eventually be expanded to "receive", but we
@@ -91,7 +116,7 @@ int ls_refs(struct repository *r, struct strvec *keys,
 
 	memset(&data, 0, sizeof(data));
 
-	git_config(ls_refs_config, NULL);
+	git_config(ls_refs_config, &data);
 
 	while (packet_reader_read(request) == PACKET_READ_NORMAL) {
 		const char *arg = request->line;
@@ -103,14 +128,35 @@ int ls_refs(struct repository *r, struct strvec *keys,
 			data.symrefs = 1;
 		else if (skip_prefix(arg, "ref-prefix ", &out))
 			strvec_push(&data.prefixes, out);
+		else if (data.allow_unborn && !strcmp("unborn", arg))
+			data.unborn = 1;
 	}
 
 	if (request->status != PACKET_READ_FLUSH)
 		die(_("expected flush after ls-refs arguments"));
 
-	head_ref_namespaced(send_ref, &data);
+	if (data.unborn)
+		send_possibly_unborn_head(&data);
+	else
+		head_ref_namespaced(send_ref, &data);
 	for_each_namespaced_ref(send_ref, &data);
 	packet_flush(1);
 	strvec_clear(&data.prefixes);
 	return 0;
 }
+
+int ls_refs_advertise(struct repository *r, struct strbuf *value)
+{
+	if (value) {
+		char *str = NULL;
+
+		if (!repo_config_get_string(the_repository, "lsrefs.unborn",
+					    &str) &&
+		    !strcmp("advertise", str)) {
+			strbuf_addstr(value, "unborn");
+			free(str);
+		}
+	}
+
+	return 1;
+}
diff --git a/ls-refs.h b/ls-refs.h
index 7b33a7c6b8..a99e4be0bd 100644
--- a/ls-refs.h
+++ b/ls-refs.h
@@ -6,5 +6,6 @@ struct strvec;
 struct packet_reader;
 int ls_refs(struct repository *r, struct strvec *keys,
 	    struct packet_reader *request);
+int ls_refs_advertise(struct repository *r, struct strbuf *value);
 
 #endif /* LS_REFS_H */
diff --git a/serve.c b/serve.c
index f6341206c4..30cb56d507 100644
--- a/serve.c
+++ b/serve.c
@@ -62,7 +62,7 @@ struct protocol_capability {
 
 static struct protocol_capability capabilities[] = {
 	{ "agent", agent_advertise, NULL },
-	{ "ls-refs", always_advertise, ls_refs },
+	{ "ls-refs", ls_refs_advertise, ls_refs },
 	{ "fetch", upload_pack_advertise, upload_pack_v2 },
 	{ "server-option", always_advertise, NULL },
 	{ "object-format", object_format_advertise, NULL },
-- 
2.29.2.684.gfbc64c5ab5-goog


  reply	other threads:[~2020-12-16  2:08 UTC|newest]

Thread overview: 109+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-08  1:31 Cloning empty repository uses locally configured default branch name Jonathan Tan
2020-12-08  2:16 ` Junio C Hamano
2020-12-08  2:32   ` brian m. carlson
2020-12-08 18:55   ` Jonathan Tan
2020-12-08 21:00     ` Junio C Hamano
2020-12-08 15:58 ` Jeff King
2020-12-08 20:06   ` Jonathan Tan
2020-12-08 21:15     ` Jeff King
2020-12-11 21:05 ` [PATCH] clone: in protocol v2, use remote's default branch Jonathan Tan
2020-12-11 23:41   ` Junio C Hamano
2020-12-14 12:38   ` Ævar Arnfjörð Bjarmason
2020-12-14 15:51     ` Felipe Contreras
2020-12-14 16:30     ` Junio C Hamano
2020-12-15  1:41       ` Ævar Arnfjörð Bjarmason
2020-12-15  2:22         ` Junio C Hamano
2020-12-15  2:38         ` Jeff King
2020-12-15  2:55           ` Junio C Hamano
2020-12-15  4:36             ` Jeff King
2020-12-16  3:09               ` Junio C Hamano
2020-12-16 18:39                 ` Jeff King
2020-12-16 20:56                   ` Junio C Hamano
2020-12-18  6:19                     ` Jeff King
2020-12-15  3:22         ` Felipe Contreras
2020-12-14 19:25     ` Jonathan Tan
2020-12-14 19:42       ` Felipe Contreras
2020-12-15  1:27   ` Jeff King
2020-12-15 19:10     ` Jonathan Tan
2020-12-16  2:07   ` [PATCH v2 0/3] Cloning with remote unborn HEAD Jonathan Tan
2020-12-16  2:07     ` Jonathan Tan [this message]
2020-12-16  6:16       ` [PATCH v2 1/3] ls-refs: report unborn targets of symrefs Junio C Hamano
2020-12-16 23:49         ` Jonathan Tan
2020-12-16 18:23       ` Jeff King
2020-12-16 23:54         ` Jonathan Tan
2020-12-17  1:32           ` Junio C Hamano
2020-12-18  6:16             ` Jeff King
2020-12-16  2:07     ` [PATCH v2 2/3] connect, transport: add no-op arg for future patch Jonathan Tan
2020-12-16  6:20       ` Junio C Hamano
2020-12-16  2:07     ` [PATCH v2 3/3] clone: respect remote unborn HEAD Jonathan Tan
2020-12-21 22:30   ` [PATCH v3 0/3] Cloning with " Jonathan Tan
2020-12-21 22:30     ` [PATCH v3 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2020-12-21 22:31     ` [PATCH v3 2/3] connect, transport: add no-op arg for future patch Jonathan Tan
2020-12-21 22:31     ` [PATCH v3 3/3] clone: respect remote unborn HEAD Jonathan Tan
2020-12-21 23:48     ` [PATCH v3 0/3] Cloning with " Junio C Hamano
2021-01-21 20:14     ` Jeff King
2020-12-22 21:54   ` [PATCH v4 " Jonathan Tan
2020-12-22 21:54     ` [PATCH v4 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2021-01-21 20:48       ` Jeff King
2021-01-26 18:13         ` Jonathan Tan
2021-01-26 23:16           ` Jeff King
2020-12-22 21:54     ` [PATCH v4 2/3] connect, transport: add no-op arg for future patch Jonathan Tan
2021-01-21 20:55       ` Jeff King
2021-01-26 18:16         ` Jonathan Tan
2020-12-22 21:54     ` [PATCH v4 3/3] clone: respect remote unborn HEAD Jonathan Tan
2021-01-21 21:02       ` Jeff King
2021-01-26 18:22         ` Jonathan Tan
2021-01-26 23:04           ` Jeff King
2021-01-28  5:50             ` Junio C Hamano
2020-12-22 22:06     ` [PATCH v4 0/3] Cloning with " Junio C Hamano
2021-01-26 18:55 ` [PATCH v5 " Jonathan Tan
2021-01-26 18:55   ` [PATCH v5 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2021-01-26 21:38     ` Junio C Hamano
2021-01-26 23:03       ` Junio C Hamano
2021-01-30  3:55         ` Jonathan Tan
2021-01-26 23:20       ` Jeff King
2021-01-26 23:38         ` Junio C Hamano
2021-01-29 20:23       ` Jonathan Tan
2021-01-29 22:04         ` Junio C Hamano
2021-02-02  2:20           ` Jonathan Tan
2021-02-02  5:00             ` Junio C Hamano
2021-01-27  1:28     ` Ævar Arnfjörð Bjarmason
2021-01-30  4:04       ` Jonathan Tan
2021-01-26 18:55   ` [PATCH v5 2/3] connect, transport: encapsulate arg in struct Jonathan Tan
2021-01-26 21:54     ` Junio C Hamano
2021-01-30  4:06       ` Jonathan Tan
2021-01-26 18:55   ` [PATCH v5 3/3] clone: respect remote unborn HEAD Jonathan Tan
2021-01-26 22:24     ` Junio C Hamano
2021-01-30  4:27       ` Jonathan Tan
2021-01-27  1:11   ` [PATCH v5 0/3] Cloning with " Junio C Hamano
2021-01-27  4:25     ` Jeff King
2021-01-27  6:14       ` Junio C Hamano
2021-01-27  1:41   ` Ævar Arnfjörð Bjarmason
2021-01-30  4:41     ` Jonathan Tan
2021-01-30 11:13       ` Ævar Arnfjörð Bjarmason
2021-02-02  2:22       ` Jonathan Tan
2021-02-03 14:23         ` Ævar Arnfjörð Bjarmason
2021-02-05 22:28     ` Junio C Hamano
2021-02-02  2:14 ` [PATCH v6 " Jonathan Tan
2021-02-02  2:14   ` [PATCH v6 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2021-02-02 16:55     ` Junio C Hamano
2021-02-02 18:34       ` Jonathan Tan
2021-02-02 22:17         ` Junio C Hamano
2021-02-03  1:04           ` Jonathan Tan
2021-02-02  2:15   ` [PATCH v6 2/3] connect, transport: encapsulate arg in struct Jonathan Tan
2021-02-02  2:15   ` [PATCH v6 3/3] clone: respect remote unborn HEAD Jonathan Tan
2021-02-05  4:58 ` [PATCH v7 0/3] Cloning with " Jonathan Tan
2021-02-05  4:58   ` [PATCH v7 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2021-02-05 16:10     ` Jeff King
2021-02-05  4:58   ` [PATCH v7 2/3] connect, transport: encapsulate arg in struct Jonathan Tan
2021-02-05  4:58   ` [PATCH v7 3/3] clone: respect remote unborn HEAD Jonathan Tan
2021-02-05  5:25   ` [PATCH v7 0/3] Cloning with " Junio C Hamano
2021-02-05 16:15     ` Jeff King
2021-02-05 21:15     ` Ævar Arnfjörð Bjarmason
2021-02-05 23:07       ` Junio C Hamano
2021-02-05 20:48 ` [PATCH v8 " Jonathan Tan
2021-02-05 20:48   ` [PATCH v8 1/3] ls-refs: report unborn targets of symrefs Jonathan Tan
2021-02-05 20:48   ` [PATCH v8 2/3] connect, transport: encapsulate arg in struct Jonathan Tan
2021-02-05 20:48   ` [PATCH v8 3/3] clone: respect remote unborn HEAD Jonathan Tan
2021-02-06 18:51   ` [PATCH v8 0/3] Cloning with " Junio C Hamano
2021-02-08 22:28     ` Junio C Hamano

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