builtin/clone.c: add --reject-shallow option

In some scenarios, users may want more history than the repository
offered for cloning, which happens to be a shallow repository, can
give them. But because users don't know it is a shallow repository
until they download it to local, we may want to refuse to clone
this kind of repository, without creating any unnecessary files.

The '--depth=x' option cannot be used as a solution; the source may
be deep enough to give us 'x' commits when cloned, but the user may
later need to deepen the history to arbitrary depth.

Teach '--reject-shallow' option to "git clone" to abort as soon as
we find out that we are cloning from a shallow repository.

Signed-off-by: Li Linchao <lilinchao@oschina.cn>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

10 files changed, 108 insertions, 6 deletions

diff --git a/Documentation/config/clone.txt b/Documentation/config/clone.txt
index 47de36a5fe..7bcfbd18a5 100644
--- a/Documentation/config/clone.txt
+++ b/Documentation/config/clone.txt
@@ -2,3 +2,7 @@ clone.defaultRemoteName::
 	The name of the remote to create when cloning a repository.  Defaults to
 	`origin`, and can be overridden by passing the `--origin` command-line
 	option to linkgit:git-clone[1].
+
+clone.rejectShallow::
+	Reject to clone a repository if it is a shallow one, can be overridden by
+	passing option `--reject-shallow` in command line. See linkgit:git-clone[1]
diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
index 02d9c19cec..3fe3810f1c 100644
--- a/Documentation/git-clone.txt
+++ b/Documentation/git-clone.txt
@@ -15,7 +15,7 @@ SYNOPSIS
 	  [--dissociate] [--separate-git-dir <git dir>]
 	  [--depth <depth>] [--[no-]single-branch] [--no-tags]
 	  [--recurse-submodules[=<pathspec>]] [--[no-]shallow-submodules]
-	  [--[no-]remote-submodules] [--jobs <n>] [--sparse]
+	  [--[no-]remote-submodules] [--jobs <n>] [--sparse] [--[no-]reject-shallow]
 	  [--filter=<filter>] [--] <repository>
 	  [<directory>]
 
@@ -149,6 +149,11 @@ objects from the source repository into a pack in the cloned repository.
 --no-checkout::
 	No checkout of HEAD is performed after the clone is complete.
 
+--[no-]reject-shallow::
+	Fail if the source repository is a shallow repository.
+	The 'clone.rejectShallow' configuration variable can be used to
+	specify the default.
+
 --bare::
 	Make a 'bare' Git repository.  That is, instead of
 	creating `<directory>` and placing the administrative
diff --git a/builtin/clone.c b/builtin/clone.c
index 51e844a2de..2a5485b724 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -50,6 +50,8 @@ static int option_no_checkout, option_bare, option_mirror, option_single_branch
 static int option_local = -1, option_no_hardlinks, option_shared;
 static int option_no_tags;
 static int option_shallow_submodules;
+static int option_reject_shallow = -1;    /* unspecified */
+static int config_reject_shallow = -1;    /* unspecified */
 static int deepen;
 static char *option_template, *option_depth, *option_since;
 static char *option_origin = NULL;
@@ -90,6 +92,8 @@ static struct option builtin_clone_options[] = {
 	OPT__VERBOSITY(&option_verbosity),
 	OPT_BOOL(0, "progress", &option_progress,
 		 N_("force progress reporting")),
+	OPT_BOOL(0, "reject-shallow", &option_reject_shallow,
+		 N_("don't clone shallow repository")),
 	OPT_BOOL('n', "no-checkout", &option_no_checkout,
 		 N_("don't create a checkout")),
 	OPT_BOOL(0, "bare", &option_bare, N_("create a bare repository")),
@@ -858,6 +862,9 @@ static int git_clone_config(const char *k, const char *v, void *cb)
 		free(remote_name);
 		remote_name = xstrdup(v);
 	}
+	if (!strcmp(k, "clone.rejectshallow"))
+		config_reject_shallow = git_config_bool(k, v);
+
 	return git_default_config(k, v, cb);
 }
 
@@ -963,6 +970,7 @@ static int path_exists(const char *path)
 int cmd_clone(int argc, const char **argv, const char *prefix)
 {
 	int is_bundle = 0, is_local;
+	int reject_shallow = 0;
 	const char *repo_name, *repo, *work_tree, *git_dir;
 	char *path, *dir, *display_repo = NULL;
 	int dest_exists, real_dest_exists = 0;
@@ -1157,6 +1165,15 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	git_config(git_clone_config, NULL);
 
 	/*
+	 * If option_reject_shallow is specified from CLI option,
+	 * ignore config_reject_shallow from git_clone_config.
+	 */
+	if (config_reject_shallow != -1)
+		reject_shallow = config_reject_shallow;
+	if (option_reject_shallow != -1)
+		reject_shallow = option_reject_shallow;
+
+	/*
 	 * apply the remote name provided by --origin only after this second
 	 * call to git_config, to ensure it overrides all config-based values.
 	 */
@@ -1216,6 +1233,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		if (filter_options.choice)
 			warning(_("--filter is ignored in local clones; use file:// instead."));
 		if (!access(mkpath("%s/shallow", path), F_OK)) {
+			if (reject_shallow)
+				die(_("source repository is shallow, reject to clone."));
 			if (option_local > 0)
 				warning(_("source repository is shallow, ignoring --local"));
 			is_local = 0;
@@ -1227,6 +1246,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 
 	transport_set_option(transport, TRANS_OPT_KEEP, "yes");
 
+	if (reject_shallow)
+		transport_set_option(transport, TRANS_OPT_REJECT_SHALLOW, "1");
 	if (option_depth)
 		transport_set_option(transport, TRANS_OPT_DEPTH,
 				     option_depth);
diff --git a/fetch-pack.c b/fetch-pack.c
index fb04a76ca2..40392692ad 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1129,9 +1129,11 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (args->deepen)
 		setup_alternate_shallow(&shallow_lock, &alternate_shallow_file,
 					NULL);
-	else if (si->nr_ours || si->nr_theirs)
+	else if (si->nr_ours || si->nr_theirs) {
+		if (args->reject_shallow_remote)
+			die(_("source repository is shallow, reject to clone."));
 		alternate_shallow_file = setup_temporary_shallow(si->shallow);
-	else
+	} else
 		alternate_shallow_file = NULL;
 	if (get_pack(args, fd, pack_lockfiles, NULL, sought, nr_sought,
 		     &gitmodules_oids))
@@ -1498,10 +1500,12 @@ static void receive_shallow_info(struct fetch_pack_args *args,
 		 * rejected (unless --update-shallow is set); do the same.
 		 */
 		prepare_shallow_info(si, shallows);
-		if (si->nr_ours || si->nr_theirs)
+		if (si->nr_ours || si->nr_theirs) {
+			if (args->reject_shallow_remote)
+				die(_("source repository is shallow, reject to clone."));
 			alternate_shallow_file =
 				setup_temporary_shallow(si->shallow);
-		else
+		} else
 			alternate_shallow_file = NULL;
 	} else {
 		alternate_shallow_file = NULL;
diff --git a/fetch-pack.h b/fetch-pack.h
index 736a3dae46..f114d72775 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -39,6 +39,7 @@ struct fetch_pack_args {
 	unsigned self_contained_and_connected:1;
 	unsigned cloning:1;
 	unsigned update_shallow:1;
+	unsigned reject_shallow_remote:1;
 	unsigned deepen:1;
 
 	/*
diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh
index e7e6c08955..329ae599fd 100755
--- a/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@ -759,6 +759,15 @@ test_expect_success 'partial clone using HTTP' '
 	partial_clone "$HTTPD_DOCUMENT_ROOT_PATH/server" "$HTTPD_URL/smart/server"
 '
 
+test_expect_success 'reject cloning shallow repository using HTTP' '
+	test_when_finished "rm -rf repo" &&
+	git clone --bare --no-local --depth=1 src "$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
+	test_must_fail git clone --reject-shallow $HTTPD_URL/smart/repo.git repo 2>err &&
+	test_i18ngrep -e "source repository is shallow, reject to clone." err &&
+
+	git clone --no-reject-shallow $HTTPD_URL/smart/repo.git repo
+'
+
 # DO NOT add non-httpd-specific tests here, because the last part of this
 # test script is only executed when httpd is available and enabled.
 
diff --git a/t/t5606-clone-options.sh b/t/t5606-clone-options.sh
index 428b0aac93..3a595c0f82 100755
--- a/t/t5606-clone-options.sh
+++ b/t/t5606-clone-options.sh
@@ -11,7 +11,8 @@ test_expect_success 'setup' '
 	mkdir parent &&
 	(cd parent && git init &&
 	 echo one >file && git add file &&
-	 git commit -m one)
+	 git commit -m one) &&
+	git clone --depth=1 --no-local parent shallow-repo
 
 '
 
@@ -45,6 +46,30 @@ test_expect_success 'disallows --bare with --separate-git-dir' '
 
 '
 
+test_expect_success 'reject cloning shallow repository' '
+	test_when_finished "rm -rf repo" &&
+	test_must_fail git clone --reject-shallow shallow-repo out 2>err &&
+	test_i18ngrep -e "source repository is shallow, reject to clone." err &&
+
+	git clone --no-reject-shallow shallow-repo repo
+'
+
+test_expect_success 'reject cloning non-local shallow repository' '
+	test_when_finished "rm -rf repo" &&
+	test_must_fail git clone --reject-shallow --no-local shallow-repo out 2>err &&
+	test_i18ngrep -e "source repository is shallow, reject to clone." err &&
+
+	git clone --no-reject-shallow --no-local shallow-repo repo
+'
+
+test_expect_success 'succeed cloning normal repository' '
+	test_when_finished "rm -rf chilad1 child2 child3 child4 " &&
+	git clone --reject-shallow parent child1 &&
+	git clone --reject-shallow --no-local parent child2 &&
+	git clone --no-reject-shallow parent child3 &&
+	git clone --no-reject-shallow --no-local parent child4
+'
+
 test_expect_success 'uses "origin" for default remote name' '
 
 	git clone parent clone-default-origin &&
diff --git a/t/t5611-clone-config.sh b/t/t5611-clone-config.sh
index 9f555b87ec..f8625f9158 100755
--- a/t/t5611-clone-config.sh
+++ b/t/t5611-clone-config.sh
@@ -95,6 +95,31 @@ test_expect_success 'clone -c remote.<remote>.fetch=<refspec> --origin=<name>' '
 	test_cmp expect actual
 '
 
+test_expect_success 'set up shallow repository' '
+	git clone --depth=1 --no-local . shallow-repo
+'
+
+test_expect_success 'clone.rejectshallow=true should reject cloning shallow repo' '
+	test_when_finished "rm -rf out" &&
+	test_must_fail git -c clone.rejectshallow=true clone --no-local shallow-repo out 2>err &&
+	test_i18ngrep -e "source repository is shallow, reject to clone." err &&
+
+	git -c clone.rejectshallow=false clone --no-local shallow-repo out
+'
+
+test_expect_success 'option --[no-]reject-shallow override clone.rejectshallow config' '
+	test_when_finished "rm -rf out" &&
+	test_must_fail git -c clone.rejectshallow=false clone --reject-shallow --no-local shallow-repo out 2>err &&
+	test_i18ngrep -e "source repository is shallow, reject to clone." err &&
+
+	git -c clone.rejectshallow=true clone --no-reject-shallow --no-local shallow-repo out
+'
+
+test_expect_success 'clone.rejectshallow=true should succeed cloning normal repo' '
+	test_when_finished "rm -rf out" &&
+	git -c clone.rejectshallow=true clone --no-local . out
+'
+
 test_expect_success MINGW 'clone -c core.hideDotFiles' '
 	test_commit attributes .gitattributes "" &&
 	rm -rf child &&
diff --git a/transport.c b/transport.c
index 1c4ab676d1..b231894f90 100644
--- a/transport.c
+++ b/transport.c
@@ -236,6 +236,9 @@ static int set_git_option(struct git_transport_options *opts,
 		list_objects_filter_die_if_populated(&opts->filter_options);
 		parse_list_objects_filter(&opts->filter_options, value);
 		return 0;
+	} else if (!strcmp(name, TRANS_OPT_REJECT_SHALLOW)) {
+		opts->reject_shallow = !!value;
+		return 0;
 	}
 	return 1;
 }
@@ -370,6 +373,7 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.stateless_rpc = transport->stateless_rpc;
 	args.server_options = transport->server_options;
 	args.negotiation_tips = data->options.negotiation_tips;
+	args.reject_shallow_remote = transport->smart_options->reject_shallow;
 
 	if (!data->got_remote_heads) {
 		int i;
diff --git a/transport.h b/transport.h
index 24e15799e7..4d5db0a7f2 100644
--- a/transport.h
+++ b/transport.h
@@ -14,6 +14,7 @@ struct git_transport_options {
 	unsigned check_self_contained_and_connected : 1;
 	unsigned self_contained_and_connected : 1;
 	unsigned update_shallow : 1;
+	unsigned reject_shallow : 1;
 	unsigned deepen_relative : 1;
 
 	/* see documentation of corresponding flag in fetch-pack.h */
@@ -194,6 +195,9 @@ void transport_check_allowed(const char *type);
 /* Aggressively fetch annotated tags if possible */
 #define TRANS_OPT_FOLLOWTAGS "followtags"
 
+/* Reject shallow repo transport */
+#define TRANS_OPT_REJECT_SHALLOW "rejectshallow"
+
 /* Accept refs that may update .git/shallow without --depth */
 #define TRANS_OPT_UPDATE_SHALLOW "updateshallow"