fetch: add --refetch option

Teach fetch and transports the --refetch option to force a full fetch
without negotiating common commits with the remote. Use when applying a
new partial clone filter to refetch all matching objects.

Signed-off-by: Robert Coup <robert@coup.net.nz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/fetch-options.txt

@@ -163,6 +163,15 @@ endif::git-pull[]
 	behavior for a remote may be specified with the remote.<name>.tagOpt
 	setting. See linkgit:git-config[1].
 
+ifndef::git-pull[]
+--refetch::
+	Instead of negotiating with the server to avoid transferring commits and
+	associated objects that are already present locally, this option fetches
+	all objects as a fresh clone would. Use this to reapply a partial clone
+	filter from configuration or using `--filter=` when the filter
+	definition has changed.
+endif::git-pull[]
+
 --refmap=<refspec>::
 	When fetching refs listed on the command line, use the
 	specified refspec (can be given more than once) to map the

builtin/fetch.c

@@ -59,7 +59,7 @@ static int prune_tags = -1; /* unspecified */
 
 static int all, append, dry_run, force, keep, multiple, update_head_ok;
 static int write_fetch_head = 1;
-static int verbosity, deepen_relative, set_upstream;
+static int verbosity, deepen_relative, set_upstream, refetch;
 static int progress = -1;
 static int enable_auto_gc = 1;
 static int tags = TAGS_DEFAULT, unshallow, update_shallow, deepen;
@@ -190,6 +190,9 @@ static struct option builtin_fetch_options[] = {
 	OPT_SET_INT_F(0, "unshallow", &unshallow,
 		      N_("convert to a complete repository"),
 		      1, PARSE_OPT_NONEG),
+	OPT_SET_INT_F(0, "refetch", &refetch,
+		      N_("re-fetch without negotiating common commits"),
+		      1, PARSE_OPT_NONEG),
 	{ OPTION_STRING, 0, "submodule-prefix", &submodule_prefix, N_("dir"),
 		   N_("prepend this to submodule path output"), PARSE_OPT_HIDDEN },
 	OPT_CALLBACK_F(0, "recurse-submodules-default",
@@ -1296,6 +1299,14 @@ static int check_exist_and_connected(struct ref *ref_map)
 	if (deepen)
 		return -1;
 
+	/*
+	 * Similarly, if we need to refetch, we always want to perform a full
+	 * fetch ignoring existing objects.
+	 */
+	if (refetch)
+		return -1;
+
+
 	/*
 	 * check_connected() allows objects to merely be promised, but
 	 * we need all direct targets to exist.
@@ -1492,6 +1503,8 @@ static struct transport *prepare_transport(struct remote *remote, int deepen)
 		set_option(transport, TRANS_OPT_DEEPEN_RELATIVE, "yes");
 	if (update_shallow)
 		set_option(transport, TRANS_OPT_UPDATE_SHALLOW, "yes");
+	if (refetch)
+		set_option(transport, TRANS_OPT_REFETCH, "yes");
 	if (filter_options.choice) {
 		const char *spec =
 			expand_list_objects_filter_spec(&filter_options);

transport-helper.c

@@ -715,6 +715,9 @@ static int fetch_refs(struct transport *transport,
 	if (data->transport_options.update_shallow)
 		set_helper_option(transport, "update-shallow", "true");
 
+	if (data->transport_options.refetch)
+		set_helper_option(transport, "refetch", "true");
+
 	if (data->transport_options.filter_options.choice) {
 		const char *spec = expand_list_objects_filter_spec(
 			&data->transport_options.filter_options);

transport.c

@@ -243,6 +243,9 @@ 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_REFETCH)) {
+		opts->refetch = !!value;
+		return 0;
 	} else if (!strcmp(name, TRANS_OPT_REJECT_SHALLOW)) {
 		opts->reject_shallow = !!value;
 		return 0;
@@ -377,6 +380,7 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.update_shallow = data->options.update_shallow;
 	args.from_promisor = data->options.from_promisor;
 	args.filter_options = data->options.filter_options;
+	args.refetch = data->options.refetch;
 	args.stateless_rpc = transport->stateless_rpc;
 	args.server_options = transport->server_options;
 	args.negotiation_tips = data->options.negotiation_tips;

transport.h

@@ -16,6 +16,7 @@ struct git_transport_options {
 	unsigned update_shallow : 1;
 	unsigned reject_shallow : 1;
 	unsigned deepen_relative : 1;
+	unsigned refetch : 1;
 
 	/* see documentation of corresponding flag in fetch-pack.h */
 	unsigned from_promisor : 1;
@@ -216,6 +217,9 @@ void transport_check_allowed(const char *type);
 /* Filter objects for partial clone and fetch */
 #define TRANS_OPT_LIST_OBJECTS_FILTER "filter"
 
+/* Refetch all objects without negotiating */
+#define TRANS_OPT_REFETCH "refetch"
+
 /* Request atomic (all-or-nothing) updates when pushing */
 #define TRANS_OPT_ATOMIC "atomic"