6 files changed, 92 insertions, 13 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 0ae4d7077b..552827935a 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -616,6 +616,24 @@ core.preferSymlinkRefs::
 	This is sometimes needed to work with old scripts that
 	expect HEAD to be a symbolic link.
 
+core.alternateRefsCommand::
+	When advertising tips of available history from an alternate, use the shell to
+	execute the specified command instead of linkgit:git-for-each-ref[1]. The
+	first argument is the absolute path of the alternate. Output must contain one
+	hex object id per line (i.e., the same as produce by `git for-each-ref
+	--format='%(objectname)'`).
++
+Note that you cannot generally put `git for-each-ref` directly into the config
+value, as it does not take a repository path as an argument (but you can wrap
+the command above in a shell script).
+
+core.alternateRefsPrefixes::
+	When listing references from an alternate, list only references that begin
+	with the given prefix. Prefixes match as if they were given as arguments to
+	linkgit:git-for-each-ref[1]. To list multiple prefixes, separate them with
+	whitespace. If `core.alternateRefsCommand` is set, setting
+	`core.alternateRefsPrefixes` has no effect.
+
 core.bare::
 	If true this repository is assumed to be 'bare' and has no
 	working directory associated with it.  If this is the case a
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 95740f4f0e..7f089be11e 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -281,8 +281,7 @@ static int show_ref_cb(const char *path_full, const struct object_id *oid,
 	return 0;
 }
 
-static void show_one_alternate_ref(const char *refname,
-				   const struct object_id *oid,
+static void show_one_alternate_ref(const struct object_id *oid,
 				   void *data)
 {
 	struct oidset *seen = data;
diff --git a/fetch-pack.c b/fetch-pack.c
index bff05ee69e..b3ed7121bc 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -76,8 +76,7 @@ struct alternate_object_cache {
 	size_t nr, alloc;
 };
 
-static void cache_one_alternate(const char *refname,
-				const struct object_id *oid,
+static void cache_one_alternate(const struct object_id *oid,
 				void *vcache)
 {
 	struct alternate_object_cache *cache = vcache;
diff --git a/t/t5410-receive-pack-alternates.sh b/t/t5410-receive-pack-alternates.sh
new file mode 100755
index 0000000000..457c20c2a5
--- /dev/null
+++ b/t/t5410-receive-pack-alternates.sh
@@ -0,0 +1,41 @@
+#!/bin/sh
+
+test_description='git receive-pack with alternate ref filtering'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit base &&
+	git clone -s --bare . fork &&
+	git checkout -b public/branch master &&
+	test_commit public &&
+	git checkout -b private/branch master &&
+	test_commit private
+'
+
+extract_haves () {
+	depacketize | perl -lne '/^(\S+) \.have/ and print $1'
+}
+
+test_expect_success 'with core.alternateRefsCommand' '
+	write_script fork/alternate-refs <<-\EOF &&
+		git --git-dir="$1" for-each-ref \
+			--format="%(objectname)" \
+			refs/heads/public/
+	EOF
+	test_config -C fork core.alternateRefsCommand alternate-refs &&
+	git rev-parse public/branch >expect &&
+	printf "0000" | git receive-pack fork >actual &&
+	extract_haves <actual >actual.haves &&
+	test_cmp expect actual.haves
+'
+
+test_expect_success 'with core.alternateRefsPrefixes' '
+	test_config -C fork core.alternateRefsPrefixes "refs/heads/private" &&
+	git rev-parse private/branch >expect &&
+	printf "0000" | git receive-pack fork >actual &&
+	extract_haves <actual >actual.haves &&
+	test_cmp expect actual.haves
+'
+
+test_done
diff --git a/transport.c b/transport.c
index 046b2f6d8c..f4ffbd96cb 100644
--- a/transport.c
+++ b/transport.c
@@ -1370,6 +1370,33 @@ literal_copy:
 	return xstrdup(url);
 }
 
+static void fill_alternate_refs_command(struct child_process *cmd,
+					const char *repo_path)
+{
+	const char *value;
+
+	if (!git_config_get_value("core.alternateRefsCommand", &value)) {
+		cmd->use_shell = 1;
+
+		argv_array_push(&cmd->args, value);
+		argv_array_push(&cmd->args, repo_path);
+	} else {
+		cmd->git_cmd = 1;
+
+		argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path);
+		argv_array_push(&cmd->args, "for-each-ref");
+		argv_array_push(&cmd->args, "--format=%(objectname)");
+
+		if (!git_config_get_value("core.alternateRefsPrefixes", &value)) {
+			argv_array_push(&cmd->args, "--");
+			argv_array_split(&cmd->args, value);
+		}
+	}
+
+	cmd->env = local_repo_env;
+	cmd->out = -1;
+}
+
 static void read_alternate_refs(const char *path,
 				alternate_ref_fn *cb,
 				void *data)
@@ -1378,12 +1405,7 @@ static void read_alternate_refs(const char *path,
 	struct strbuf line = STRBUF_INIT;
 	FILE *fh;
 
-	cmd.git_cmd = 1;
-	argv_array_pushf(&cmd.args, "--git-dir=%s", path);
-	argv_array_push(&cmd.args, "for-each-ref");
-	argv_array_push(&cmd.args, "--format=%(objectname) %(refname)");
-	cmd.env = local_repo_env;
-	cmd.out = -1;
+	fill_alternate_refs_command(&cmd, path);
 
 	if (start_command(&cmd))
 		return;
@@ -1393,13 +1415,13 @@ static void read_alternate_refs(const char *path,
 		struct object_id oid;
 
 		if (get_oid_hex(line.buf, &oid) ||
-		    line.buf[GIT_SHA1_HEXSZ] != ' ') {
+		    line.buf[GIT_SHA1_HEXSZ]) {
 			warning(_("invalid line while parsing alternate refs: %s"),
 				line.buf);
 			break;
 		}
 
-		cb(line.buf + GIT_SHA1_HEXSZ + 1, &oid, data);
+		cb(&oid, data);
 	}
 
 	fclose(fh);
diff --git a/transport.h b/transport.h
index 01e717c29e..9baeca2d7a 100644
--- a/transport.h
+++ b/transport.h
@@ -261,6 +261,6 @@ int transport_refs_pushed(struct ref *ref);
 void transport_print_push_status(const char *dest, struct ref *refs,
 		  int verbose, int porcelain, unsigned int *reject_reasons);
 
-typedef void alternate_ref_fn(const char *refname, const struct object_id *oid, void *);
+typedef void alternate_ref_fn(const struct object_id *oid, void *);
 extern void for_each_alternate_ref(alternate_ref_fn, void *);
 #endif