Merge branch 'jc/hidden-refs'

Allow the server side to redact the refs/ namespace it shows to the
client.

Will merge to 'master'.

* jc/hidden-refs:
  upload/receive-pack: allow hiding ref hierarchies
  upload-pack: simplify request validation
  upload-pack: share more code

7 files changed, 166 insertions, 30 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 9b1159738..481736a47 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1880,6 +1880,15 @@ receive.denyNonFastForwards::
 	even if that push is forced. This configuration variable is
 	set when initializing a shared repository.
 
+receive.hiderefs::
+	String(s) `receive-pack` uses to decide which refs to omit
+	from its initial advertisement.  Use more than one
+	definitions to specify multiple prefix strings. A ref that
+	are under the hierarchies listed on the value of this
+	variable is excluded, and is hidden when responding to `git
+	push`, and an attempt to update or delete a hidden ref by
+	`git push` is rejected.
+
 receive.updateserverinfo::
 	If set to true, git-receive-pack will run git-update-server-info
 	after receiving data from git-push and updating refs.
@@ -2092,11 +2101,25 @@ transfer.fsckObjects::
 	not set, the value of this variable is used instead.
 	Defaults to false.
 
+transfer.hiderefs::
+	This variable can be used to set both `receive.hiderefs`
+	and `uploadpack.hiderefs` at the same time to the same
+	values.  See entries for these other variables.
+
 transfer.unpackLimit::
 	When `fetch.unpackLimit` or `receive.unpackLimit` are
 	not set, the value of this variable is used instead.
 	The default value is 100.
 
+uploadpack.hiderefs::
+	String(s) `upload-pack` uses to decide which refs to omit
+	from its initial advertisement.  Use more than one
+	definitions to specify multiple prefix strings. A ref that
+	are under the hierarchies listed on the value of this
+	variable is excluded, and is hidden from `git ls-remote`,
+	`git fetch`, etc.  An attempt to fetch a hidden ref by `git
+	fetch` will fail.
+
 url.<base>.insteadOf::
 	Any URL that starts with this value will be rewritten to
 	start, instead, with <base>. In cases where some site serves a
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e8878de45..62ba6e7a3 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -59,6 +59,11 @@ static enum deny_action parse_deny_action(const char *var, const char *value)
 
 static int receive_pack_config(const char *var, const char *value, void *cb)
 {
+	int status = parse_hide_refs_config(var, value, "receive");
+
+	if (status)
+		return status;
+
 	if (strcmp(var, "receive.denydeletes") == 0) {
 		deny_deletes = git_config_bool(var, value);
 		return 0;
@@ -119,6 +124,9 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 
 static void show_ref(const char *path, const unsigned char *sha1)
 {
+	if (ref_is_hidden(path))
+		return;
+
 	if (sent_capabilities)
 		packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
 	else
@@ -685,6 +693,20 @@ static int iterate_receive_command_list(void *cb_data, unsigned char sha1[20])
 	return -1; /* end of list */
 }
 
+static void reject_updates_to_hidden(struct command *commands)
+{
+	struct command *cmd;
+
+	for (cmd = commands; cmd; cmd = cmd->next) {
+		if (cmd->error_string || !ref_is_hidden(cmd->ref_name))
+			continue;
+		if (is_null_sha1(cmd->new_sha1))
+			cmd->error_string = "deny deleting a hidden ref";
+		else
+			cmd->error_string = "deny updating a hidden ref";
+	}
+}
+
 static void execute_commands(struct command *commands, const char *unpacker_error)
 {
 	struct command *cmd;
@@ -701,6 +723,8 @@ static void execute_commands(struct command *commands, const char *unpacker_erro
 				       0, &cmd))
 		set_connectivity_errors(commands);
 
+	reject_updates_to_hidden(commands);
+
 	if (run_receive_hook(commands, "pre-receive", 0)) {
 		for (cmd = commands; cmd; cmd = cmd->next) {
 			if (!cmd->error_string)
diff --git a/refs.c b/refs.c
index 296282530..175b9fcaa 100644
--- a/refs.c
+++ b/refs.c
@@ -3,6 +3,7 @@
 #include "object.h"
 #include "tag.h"
 #include "dir.h"
+#include "string-list.h"
 
 /*
  * Make sure "ref" is something reasonable to have under ".git/refs/";
@@ -2554,3 +2555,46 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
 	free(short_name);
 	return xstrdup(refname);
 }
+
+static struct string_list *hide_refs;
+
+int parse_hide_refs_config(const char *var, const char *value, const char *section)
+{
+	if (!strcmp("transfer.hiderefs", var) ||
+	    /* NEEDSWORK: use parse_config_key() once both are merged */
+	    (!prefixcmp(var, section) && var[strlen(section)] == '.' &&
+	     !strcmp(var + strlen(section), ".hiderefs"))) {
+		char *ref;
+		int len;
+
+		if (!value)
+			return config_error_nonbool(var);
+		ref = xstrdup(value);
+		len = strlen(ref);
+		while (len && ref[len - 1] == '/')
+			ref[--len] = '\0';
+		if (!hide_refs) {
+			hide_refs = xcalloc(1, sizeof(*hide_refs));
+			hide_refs->strdup_strings = 1;
+		}
+		string_list_append(hide_refs, ref);
+	}
+	return 0;
+}
+
+int ref_is_hidden(const char *refname)
+{
+	struct string_list_item *item;
+
+	if (!hide_refs)
+		return 0;
+	for_each_string_list_item(item, hide_refs) {
+		int len;
+		if (prefixcmp(refname, item->string))
+			continue;
+		len = strlen(item->string);
+		if (!refname[len] || refname[len] == '/')
+			return 1;
+	}
+	return 0;
+}
diff --git a/refs.h b/refs.h
index d6c2fe2df..1b2e2d3a9 100644
--- a/refs.h
+++ b/refs.h
@@ -147,4 +147,7 @@ int update_ref(const char *action, const char *refname,
 		const unsigned char *sha1, const unsigned char *oldval,
 		int flags, enum action_on_err onerr);
 
+extern int parse_hide_refs_config(const char *var, const char *value, const char *);
+extern int ref_is_hidden(const char *);
+
 #endif /* REFS_H */
diff --git a/t/t5512-ls-remote.sh b/t/t5512-ls-remote.sh
index d16e5d384..321c3e523 100755
--- a/t/t5512-ls-remote.sh
+++ b/t/t5512-ls-remote.sh
@@ -126,4 +126,16 @@ test_expect_success 'Report match with --exit-code' '
 	test_cmp expect actual
 '
 
+for configsection in transfer uploadpack
+do
+	test_expect_success "Hide some refs with $configsection.hiderefs" '
+		test_config $configsection.hiderefs refs/tags &&
+		git ls-remote . >actual &&
+		test_unconfig $configsection.hiderefs &&
+		git ls-remote . |
+		sed -e "/	refs\/tags\//d" >expect &&
+		test_cmp expect actual
+	'
+done
+
 test_done
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 8f024a08f..c31e5c1c5 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -1016,4 +1016,31 @@ test_expect_success 'push --prune refspec' '
 	! check_push_result $the_first_commit tmp/foo tmp/bar
 '
 
+for configsection in transfer receive
+do
+	test_expect_success "push to update a ref hidden by $configsection.hiderefs" '
+		mk_test heads/master hidden/one hidden/two hidden/three &&
+		(
+			cd testrepo &&
+			git config $configsection.hiderefs refs/hidden
+		) &&
+
+		# push to unhidden ref succeeds normally
+		git push testrepo master:refs/heads/master &&
+		check_push_result $the_commit heads/master &&
+
+		# push to update a hidden ref should fail
+		test_must_fail git push testrepo master:refs/hidden/one &&
+		check_push_result $the_first_commit hidden/one &&
+
+		# push to delete a hidden ref should fail
+		test_must_fail git push testrepo :refs/hidden/two &&
+		check_push_result $the_first_commit hidden/two &&
+
+		# idempotent push to update a hidden ref should fail
+		test_must_fail git push testrepo $the_first_commit:refs/hidden/three &&
+		check_push_result $the_first_commit hidden/three
+	'
+done
+
 test_done
diff --git a/upload-pack.c b/upload-pack.c
index 7c05b15e6..30146a04f 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -12,6 +12,7 @@
 #include "run-command.h"
 #include "sigchain.h"
 #include "version.h"
+#include "string-list.h"
 
 static const char upload_pack_usage[] = "git upload-pack [--strict] [--timeout=<n>] <dir>";
 
@@ -28,7 +29,7 @@ static const char upload_pack_usage[] = "git upload-pack [--strict] [--timeout=<
 
 static unsigned long oldest_have;
 
-static int multi_ack, nr_our_refs;
+static int multi_ack;
 static int no_done;
 static int use_thin_pack, use_ofs_delta, use_include_tag;
 static int no_progress, daemon_mode;
@@ -139,7 +140,6 @@ static void create_pack_file(void)
 {
 	struct async rev_list;
 	struct child_process pack_objects;
-	int create_full_pack = (nr_our_refs == want_obj.nr && !have_obj.nr);
 	char data[8193], progress[128];
 	char abort_msg[] = "aborting due to possible repository "
 		"corruption on the remote side.";
@@ -151,9 +151,7 @@ static void create_pack_file(void)
 	argv[arg++] = "pack-objects";
 	if (!shallow_nr) {
 		argv[arg++] = "--revs";
-		if (create_full_pack)
-			argv[arg++] = "--all";
-		else if (use_thin_pack)
+		if (use_thin_pack)
 			argv[arg++] = "--thin";
 	}
 
@@ -185,15 +183,15 @@ static void create_pack_file(void)
 	}
 	else {
 		FILE *pipe_fd = xfdopen(pack_objects.in, "w");
-		if (!create_full_pack) {
-			int i;
-			for (i = 0; i < want_obj.nr; i++)
-				fprintf(pipe_fd, "%s\n", sha1_to_hex(want_obj.objects[i].item->sha1));
-			fprintf(pipe_fd, "--not\n");
-			for (i = 0; i < have_obj.nr; i++)
-				fprintf(pipe_fd, "%s\n", sha1_to_hex(have_obj.objects[i].item->sha1));
-		}
+		int i;
 
+		for (i = 0; i < want_obj.nr; i++)
+			fprintf(pipe_fd, "%s\n",
+				sha1_to_hex(want_obj.objects[i].item->sha1));
+		fprintf(pipe_fd, "--not\n");
+		for (i = 0; i < have_obj.nr; i++)
+			fprintf(pipe_fd, "%s\n",
+				sha1_to_hex(have_obj.objects[i].item->sha1));
 		fprintf(pipe_fd, "\n");
 		fflush(pipe_fd);
 		fclose(pipe_fd);
@@ -729,15 +727,30 @@ static void receive_needs(void)
 	free(shallows.objects);
 }
 
+/* return non-zero if the ref is hidden, otherwise 0 */
+static int mark_our_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
+{
+	struct object *o = lookup_unknown_object(sha1);
+
+	if (ref_is_hidden(refname))
+		return 1;
+	if (!o)
+		die("git upload-pack: cannot find object %s:", sha1_to_hex(sha1));
+	o->flags |= OUR_REF;
+	return 0;
+}
+
 static int send_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
 	static const char *capabilities = "multi_ack thin-pack side-band"
 		" side-band-64k ofs-delta shallow no-progress"
 		" include-tag multi_ack_detailed";
-	struct object *o = lookup_unknown_object(sha1);
 	const char *refname_nons = strip_namespace(refname);
 	unsigned char peeled[20];
 
+	if (mark_our_ref(refname, sha1, flag, cb_data))
+		return 0;
+
 	if (capabilities)
 		packet_write(1, "%s %s%c%s%s agent=%s\n",
 			     sha1_to_hex(sha1), refname_nons,
@@ -747,27 +760,11 @@ static int send_ref(const char *refname, const unsigned char *sha1, int flag, vo
 	else
 		packet_write(1, "%s %s\n", sha1_to_hex(sha1), refname_nons);
 	capabilities = NULL;
-	if (!(o->flags & OUR_REF)) {
-		o->flags |= OUR_REF;
-		nr_our_refs++;
-	}
 	if (!peel_ref(refname, peeled))
 		packet_write(1, "%s %s^{}\n", sha1_to_hex(peeled), refname_nons);
 	return 0;
 }
 
-static int mark_our_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
-{
-	struct object *o = parse_object(sha1);
-	if (!o)
-		die("git upload-pack: cannot find object %s:", sha1_to_hex(sha1));
-	if (!(o->flags & OUR_REF)) {
-		o->flags |= OUR_REF;
-		nr_our_refs++;
-	}
-	return 0;
-}
-
 static void upload_pack(void)
 {
 	if (advertise_refs || !stateless_rpc) {
@@ -789,6 +786,11 @@ static void upload_pack(void)
 	}
 }
 
+static int upload_pack_config(const char *var, const char *value, void *unused)
+{
+	return parse_hide_refs_config(var, value, "uploadpack");
+}
+
 int main(int argc, char **argv)
 {
 	char *dir;
@@ -840,6 +842,7 @@ int main(int argc, char **argv)
 		die("'%s' does not appear to be a git repository", dir);
 	if (is_repository_shallow())
 		die("attempt to fetch/clone from a shallow repository");
+	git_config(upload_pack_config, NULL);
 	if (getenv("GIT_DEBUG_SEND_PACK"))
 		debug_fd = atoi(getenv("GIT_DEBUG_SEND_PACK"));
 	upload_pack();