[PATCH v3 15/28] fetch: add --update-shallow to get refs that require updating .git/shallow

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/fetch-options.txt |  6 ++++++
 builtin/fetch.c                 |  6 +++++-
 fetch-pack.c                    | 26 ++++++++++++++++++++++++++
 fetch-pack.h                    |  1 +
 t/t5536-fetch-shallow.sh        | 22 ++++++++++++++++++++++
 transport.c                     |  4 ++++
 transport.h                     |  4 ++++
 7 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index a83d2b4..54043e3 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -21,6 +21,12 @@
 If the source repository is shallow, fetch as much as possible so that
 the current repository has the same history as the source repository.
 
+--update-shallow::
+	By default when fetching from a shallow repository,
+	`git fetch` refuses refs that require updating
+	.git/shallow. This option updates .git/shallow and accept such
+	refs.
+
 ifndef::git-pull[]
 --dry-run::
 	Show what would be done, without making any changes.
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 7b41a7e..d2e4fc0 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -36,7 +36,7 @@ static int prune = -1; /* unspecified */
 
 static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity;
 static int progress = -1, recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
-static int tags = TAGS_DEFAULT, unshallow;
+static int tags = TAGS_DEFAULT, unshallow, update_shallow;
 static const char *depth;
 static const char *upload_pack;
 static struct strbuf default_rla = STRBUF_INIT;
@@ -104,6 +104,8 @@ static struct option builtin_fetch_options[] = {
 	{ OPTION_STRING, 0, "recurse-submodules-default",
 		   &recurse_submodules_default, NULL,
 		   N_("default mode for recursion"), PARSE_OPT_HIDDEN },
+	OPT_BOOL(0, "update-shallow", &update_shallow,
+		 N_("accept refs that update .git/shallow")),
 	OPT_END()
 };
 
@@ -768,6 +770,8 @@ static struct transport *prepare_transport(struct remote *remote)
 		set_option(transport, TRANS_OPT_KEEP, "yes");
 	if (depth)
 		set_option(transport, TRANS_OPT_DEPTH, depth);
+	if (update_shallow)
+		set_option(transport, TRANS_OPT_UPDATE_SHALLOW, "yes");
 	return transport;
 }
 
diff --git a/fetch-pack.c b/fetch-pack.c
index 64fa5d2..82aa5db 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -995,6 +995,32 @@ static void update_shallow(struct fetch_pack_args *args,
 	for (i = 0; i < nr_sought; i++)
 		add_extra_have(&ref, sought[i]->old_sha1);
 
+	if (args->update_shallow) {
+		/*
+		 * remote is also shallow, .git/shallow may be updated
+		 * so all refs can be accepted. Make sure we only add
+		 * shallow roots that are actually reachable from new
+		 * refs.
+		 */
+		uint32_t **used = xmalloc(sizeof(*used) * shallow->nr);
+		if (mark_new_shallow_refs(&ref, NULL, used, shallow)) {
+			struct extra_have_objects extra;
+			memset(&extra, 0, sizeof(extra));
+			for (i = 0; i < shallow->nr; i++)
+				if (used[i])
+					add_extra_have(&extra,
+						       shallow->array[i]);
+			setup_alternate_shallow(&shallow_lock,
+						&alternate_shallow_file,
+						&extra);
+			commit_lock_file(&shallow_lock);
+			free(extra.array);
+		}
+		free(used);
+		free(ref.array);
+		return;
+	}
+
 	status = xcalloc(nr_sought, sizeof(*status));
 
 	/*
diff --git a/fetch-pack.h b/fetch-pack.h
index cabfb60..5cfb77b 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -23,6 +23,7 @@ struct fetch_pack_args {
 	unsigned check_self_contained_and_connected:1;
 	unsigned self_contained_and_connected:1;
 	unsigned cloning:1;
+	unsigned update_shallow:1;
 };
 
 /*
diff --git a/t/t5536-fetch-shallow.sh b/t/t5536-fetch-shallow.sh
index e011ead..95b6313 100755
--- a/t/t5536-fetch-shallow.sh
+++ b/t/t5536-fetch-shallow.sh
@@ -141,4 +141,26 @@ EOF
 	)
 '
 
+test_expect_success 'fetch --update-shallow' '
+	(
+	cd notshallow &&
+	git fetch --update-shallow ../shallow/.git refs/heads/*:refs/remotes/shallow/* &&
+	git fsck &&
+	git for-each-ref --format="%(refname)" |sort >actual.refs &&
+	cat <<EOF >expect.refs &&
+refs/remotes/shallow/master
+refs/remotes/shallow/no-shallow
+EOF
+	test_cmp expect.refs actual.refs &&
+	git log --format=%s shallow/master >actual &&
+	cat <<EOF >expect &&
+6
+5
+4
+3
+EOF
+	test_cmp expect actual
+	)
+'
+
 test_done
diff --git a/transport.c b/transport.c
index d6d14eb..c0be6b1 100644
--- a/transport.c
+++ b/transport.c
@@ -476,6 +476,9 @@ static int set_git_option(struct git_transport_options *opts,
 	} else if (!strcmp(name, TRANS_OPT_KEEP)) {
 		opts->keep = !!value;
 		return 0;
+	} else if (!strcmp(name, TRANS_OPT_UPDATE_SHALLOW)) {
+		opts->update_shallow = !!value;
+		return 0;
 	} else if (!strcmp(name, TRANS_OPT_DEPTH)) {
 		if (!value)
 			opts->depth = 0;
@@ -542,6 +545,7 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.check_self_contained_and_connected =
 		data->options.check_self_contained_and_connected;
 	args.cloning = transport->cloning;
+	args.update_shallow = data->options.update_shallow;
 
 	if (!data->got_remote_heads) {
 		connect_setup(transport, 0, 0);
diff --git a/transport.h b/transport.h
index 59842d4..02ea248 100644
--- a/transport.h
+++ b/transport.h
@@ -11,6 +11,7 @@ struct git_transport_options {
 	unsigned followtags : 1;
 	unsigned check_self_contained_and_connected : 1;
 	unsigned self_contained_and_connected : 1;
+	unsigned update_shallow : 1;
 	int depth;
 	const char *uploadpack;
 	const char *receivepack;
@@ -152,6 +153,9 @@ struct transport *transport_get(struct remote *, const char *);
 /* Aggressively fetch annotated tags if possible */
 #define TRANS_OPT_FOLLOWTAGS "followtags"
 
+/* Accept refs that may update .git/shallow without --depth */
+#define TRANS_OPT_UPDATE_SHALLOW "updateshallow"
+
 /**
  * Returns 0 if the option was used, non-zero otherwise. Prints a
  * message to stderr if the option is not used.
-- 
1.8.2.83.gc99314b