[PATCH v6 36/40] clone: add --initial-refspec option

[Christian Couder <christian.couder@gmail.com>]

This option makes it possible to separate fetching refs when cloning
in two parts, an initial part and a later normal part.

This way after the initial part, mechanisms like the external odb
mechanism can be used to prefetch some objects using information
that has been made available during the initial fetch.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 builtin/clone.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index 2e5d60521d..57cecd194c 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -57,6 +57,7 @@ static enum transport_family family;
 static struct string_list option_config = STRING_LIST_INIT_NODUP;
 static struct string_list option_required_reference = STRING_LIST_INIT_NODUP;
 static struct string_list option_optional_reference = STRING_LIST_INIT_NODUP;
+static struct string_list option_initial_refspec = STRING_LIST_INIT_NODUP;
 static int option_dissociate;
 static int max_jobs = -1;
 static struct string_list option_recurse_submodules = STRING_LIST_INIT_NODUP;
@@ -107,6 +108,8 @@ static struct option builtin_clone_options[] = {
 			N_("reference repository")),
 	OPT_STRING_LIST(0, "reference-if-able", &option_optional_reference,
 			N_("repo"), N_("reference repository")),
+	OPT_STRING_LIST(0, "initial-refspec", &option_initial_refspec,
+			N_("refspec"), N_("fetch this refspec first")),
 	OPT_BOOL(0, "dissociate", &option_dissociate,
 		 N_("use --reference only while cloning")),
 	OPT_STRING('o', "origin", &option_origin, N_("name"),
@@ -869,6 +872,47 @@ static void dissociate_from_references(void)
 	free(alternates);
 }
 
+static struct refspec *parse_initial_refspecs(void)
+{
+	const char **refspecs;
+	struct refspec *initial_refspecs;
+	struct string_list_item *rs;
+	int i = 0;
+
+	if (!option_initial_refspec.nr)
+		return NULL;
+
+	refspecs = xcalloc(option_initial_refspec.nr, sizeof(const char *));
+
+	for_each_string_list_item(rs, &option_initial_refspec)
+		refspecs[i++] = rs->string;
+
+	initial_refspecs = parse_fetch_refspec(option_initial_refspec.nr, refspecs);
+
+	free(refspecs);
+
+	return initial_refspecs;
+}
+
+static void fetch_initial_refs(struct transport *transport,
+			       const struct ref *refs,
+			       struct refspec *initial_refspecs,
+			       const char *branch_top,
+			       const char *reflog_msg,
+			       int is_local)
+{
+	int i;
+
+	for (i = 0; i < option_initial_refspec.nr; i++) {
+		struct ref *init_refs = NULL;
+		struct ref **tail = &init_refs;
+		get_fetch_map(refs, &initial_refspecs[i], &tail, 0);
+		transport_fetch_refs(transport, init_refs);
+		update_remote_refs(refs, init_refs, NULL, branch_top, reflog_msg,
+				   transport, !is_local, 1);
+	}
+}
+
 int cmd_clone(int argc, const char **argv, const char *prefix)
 {
 	int is_bundle = 0, is_local;
@@ -892,6 +936,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	struct refspec *refspec;
 	const char *fetch_pattern;
 
+	struct refspec *initial_refspecs;
+	int is_initial;
+
 	packet_trace_identity("clone");
 	argc = parse_options(argc, argv, prefix, builtin_clone_options,
 			     builtin_clone_usage, 0);
@@ -1059,6 +1106,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (option_required_reference.nr || option_optional_reference.nr)
 		setup_reference();
 
+	initial_refspecs = parse_initial_refspecs();
+
 	fetch_pattern = xstrfmt("+%s*:%s*", src_ref_prefix, branch_top.buf);
 	refspec = parse_fetch_refspec(1, &fetch_pattern);
 	free((char *)fetch_pattern);
@@ -1114,6 +1163,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	refs = transport_get_remote_refs(transport);
 
 	if (refs) {
+		fetch_initial_refs(transport, refs, initial_refspecs,
+				   branch_top.buf, reflog_msg.buf, is_local);
+
 		mapped_refs = wanted_peer_refs(refs, refspec);
 		/*
 		 * transport_get_remote_refs() may return refs with null sha-1
@@ -1173,9 +1225,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	else if (refs && complete_refs_before_fetch)
 		transport_fetch_refs(transport, mapped_refs);
 
+	is_initial = !refs || option_initial_refspec.nr == 0;
 	update_remote_refs(refs, mapped_refs, remote_head_points_at,
 			   branch_top.buf, reflog_msg.buf, transport,
-			   !is_local, 0);
+			   !is_local, is_initial);
 
 	update_head(our_head_points_at, remote_head, reflog_msg.buf);
 
-- 
2.14.1.576.g3f707d88cd