Merge pull request #228: "gvfs-helper prefetch" during "git fetch"

This is a follow-up to #227.

1. When a new flag is added to our Git config, we can run `gvfs-helper prefetch` inside of our `git fetch` calls. This will help ensure we have updated commits and trees even if the background prefetches have fallen behind (or are not running).

2. With a new `--no-update-remote-refs` we can avoid updating the `refs/remotes` namespace. This will allow us to run `git fetch --all --no-update-remote-refs +refs/heads/*:refs/hidden/*` and we will get the new refs into a local folder (that doesn't appear anywhere). The most important thing is that users will still see when their remote refs update.

Documentation/config/core.txt

@@ -659,6 +659,10 @@ core.gvfs::
 		is first accessed and brought down to the client. Git.exe can't
 		currently tell the first access vs subsequent accesses so this
 		flag just blocks them from occurring at all.
+	GVFS_PREFETCH_DURING_FETCH::
+		Bit value 128
+		While performing a `git fetch` command, use the gvfs-helper to
+		perform a "prefetch" of commits and trees.
 --
 
 core.useGvfsHelper::

Documentation/fetch-options.txt

@@ -254,6 +254,11 @@ endif::git-pull[]
 	'git-pull' the --ff-only option will still check for forced updates
 	before attempting a fast-forward update. See linkgit:git-config[1].
 
+--no-update-remote-refs::
+	By default, git updates the `refs/remotes/` refspace with the refs
+	advertised by the remotes during a `git fetch` command. With this
+	option, those refs will be ignored.
+
 -4::
 --ipv4::
 	Use IPv4 addresses only, ignoring IPv6 addresses.

builtin/fetch.c

@@ -27,6 +27,8 @@
 #include "branch.h"
 #include "promisor-remote.h"
 #include "commit-graph.h"
+#include "gvfs.h"
+#include "gvfs-helper-client.h"
 
 #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
 
@@ -78,6 +80,7 @@ static struct list_objects_filter_options filter_options;
 static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;
+static int update_remote_refs = 1;
 
 static int git_fetch_config(const char *k, const char *v, void *cb)
 {
@@ -201,6 +204,8 @@ static struct option builtin_fetch_options[] = {
 		 N_("check for forced-updates on all updated branches")),
 	OPT_BOOL(0, "write-commit-graph", &fetch_write_commit_graph,
 		 N_("write the commit-graph after fetching")),
+	OPT_BOOL(0, "update-remote-refs", &update_remote_refs,
+		 N_("update the refs/remotes/ refspace")),
 	OPT_END()
 };
 
@@ -746,6 +751,9 @@ static int update_local_ref(struct ref *ref,
 	const char *pretty_ref = prettify_refname(ref->name);
 	int fast_forward = 0;
 
+	if (!update_remote_refs && starts_with(ref->name, "refs/remotes/"))
+		return 0;
+
 	type = oid_object_info(the_repository, &ref->new_oid, NULL);
 	if (type < 0)
 		die(_("object %s not found"), oid_to_hex(&ref->new_oid));
@@ -1821,6 +1829,9 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 		}
 	}
 
+	if (core_gvfs & GVFS_PREFETCH_DURING_FETCH)
+		gh_client__prefetch(0, NULL);
+
 	if (remote) {
 		if (filter_options.choice || has_promisor_remote())
 			fetch_one_setup_partial(remote);

gvfs.h

@@ -17,6 +17,7 @@
 #define GVFS_NO_DELETE_OUTSIDE_SPARSECHECKOUT       (1 << 3)
 #define GVFS_FETCH_SKIP_REACHABILITY_AND_UPLOADPACK (1 << 4)
 #define GVFS_BLOCK_FILTERS_AND_EOL_CONVERSIONS      (1 << 6)
+#define GVFS_PREFETCH_DURING_FETCH		    (1 << 7)
 
 void gvfs_load_config_value(const char *value);
 int gvfs_config_is_set(int mask);