sha1-file: create shared-cache directory if it doesn't exist

The config variable `gvfs.sharedCache` contains the pathname to an alternate
<odb> that will be used by `gvfs-helper` to store dynamically-fetched missing
objects.  If this directory does not exist on disk, `prepare_alt_odb()` omits
this directory from the in-memory list of alternates.  This causes `git`
commands (and `gvfs-helper` in particular) to fall-back to `.git/objects` for
storage of these objects.  This disables the shared-cache and leads to poorer
performance.

Teach `alt_obj_usable()` and `prepare_alt_odb()`, match up the directory
named in `gvfs.sharedCache` with an entry in `.git/objects/info/alternates`
and force-create the `<odb>` root directory (and the associated `<odb>/pack`
directory) if necessary.

If the value of `gvfs.sharedCache` refers to a directory that is NOT listed
as an alternate, create an in-memory alternate entry in the odb-list.  (This
is similar to how GIT_ALTERNATE_OBJECT_DIRECTORIES works.)

This work happens the first time that `prepare_alt_odb()` is called.

Furthermore, teach the `--shared-cache=<odb>` command line option in
`gvfs-helper` (which is runs after the first call to `prepare_alt_odb()`)
to override the inherited shared-cache (and again, create the ODB directory
if necessary).

Signed-off-by: Jeff Hostetler <[email protected]>

Author: jeffhostetler

gvfs-helper.c

@@ -690,7 +690,7 @@ static int option_parse_shared_cache_directory(const struct option *opt,
 		 */
 		strbuf_addbuf(&gvfs_shared_cache_pathname, &buf_arg);
 
-		add_to_alternates_memory(buf_arg.buf);
+		odb_add_to_alternates_memory(the_repository->objects, buf_arg.buf);
 
 		strbuf_release(&buf_arg);
 		return 0;
@@ -709,7 +709,7 @@ static int option_parse_shared_cache_directory(const struct option *opt,
 		strbuf_setlen(&gvfs_shared_cache_pathname, 0);
 		strbuf_addbuf(&gvfs_shared_cache_pathname, &buf_arg);
 
-		add_to_alternates_memory(buf_arg.buf);
+		odb_add_to_alternates_memory(the_repository->objects, buf_arg.buf);
 
 		/*
 		 * alt_odb_usable() releases gvfs_shared_cache_pathname
@@ -1037,7 +1037,7 @@ static void select_odb(void)
 			      &gvfs_shared_cache_pathname);
 	else
 		strbuf_addstr(&gh__global.buf_odb_path,
-			      the_repository->objects->odb->path);
+			      the_repository->objects->sources->path);
 }
 
 /*

odb.c

@@ -100,6 +100,7 @@ static int alt_odb_usable(struct object_database *o,
 			  struct strbuf *path,
 			  const char *normalized_objdir, khiter_t *pos)
 {
+	extern struct strbuf gvfs_shared_cache_pathname;
 	int r;
 
 	if (!strbuf_cmp(path, &gvfs_shared_cache_pathname)) {
@@ -123,7 +124,7 @@ static int alt_odb_usable(struct object_database *o,
 		 */
 		strbuf_addf(&buf_pack_foo, "%s/pack/foo", path->buf);
 
-		scld = safe_create_leading_directories(the_repository, buf_pack_foo.buf);
+		scld = safe_create_leading_directories(o->repo, buf_pack_foo.buf);
 		if (scld != SCLD_OK && scld != SCLD_EXISTS) {
 			error_errno(_("could not create shared-cache ODB '%s'"),
 				    gvfs_shared_cache_pathname.buf);
@@ -648,12 +649,14 @@ int odb_for_each_alternate(struct object_database *odb,
 
 void odb_prepare_alternates(struct object_database *odb)
 {
+	extern struct strbuf gvfs_shared_cache_pathname;
+
 	if (odb->loaded_alternates)
 		return;
 
 	link_alt_odb_entries(odb, odb->alternate_db, PATH_SEP, NULL, 0);
 
-	read_info_alternates(r, r->objects->odb->path, 0);
+	read_info_alternates(odb, odb->repo->objects->sources->path, 0);
 
 	if (gvfs_shared_cache_pathname.len &&
 	    !gvfs_matched_shared_cache_to_alternate) {
@@ -677,11 +680,11 @@ void odb_prepare_alternates(struct object_database *odb)
 		 * for us to update .git/objects/info/alternates instead.
 		 * The code here is considered a backstop.
 		 */
-		link_alt_odb_entries(r, gvfs_shared_cache_pathname.buf,
+		link_alt_odb_entries(odb, gvfs_shared_cache_pathname.buf,
 				     '\n', NULL, 0);
 	}
 
-	r->objects->loaded_alternates = 1;
+	odb->repo->objects->loaded_alternates = 1;
 }
 
 int odb_has_alternates(struct object_database *odb)