core.fsync: sync loose objects by default on windows

Git for Windows has defaulted to core.fsyncObjectFiles=true since
September 2017.  Preceding commits in this series eliminated the
core.fsyncObjectFiles setting, so this commit implements equivalent
behavior.

Loose object file syncing was previously only enabled in the Git for
Windows fork, but now I am setting it in upstream Git so that we can get
coverage for batch mode syncing.

Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>

Documentation/config/core.txt

@@ -564,7 +564,7 @@ core.fsync::
 * `index` hardens the index when it is modified.
 * `objects` is an aggregate option that includes `loose-objects` and `pack`.
 * `derived-metadata` is an aggregate option that includes `pack-metadata` and `commit-graph`.
-* `default` is an aggregate option that is equivalent to `objects,derived-metadata,-loose-object`
+* `default` is an aggregate option that represents the platform-specific default
 * `all` is an aggregate option that syncs all individual components above.
 
 core.fsyncMethod::

cache.h

@@ -1007,9 +1007,14 @@ enum fsync_component {
 	FSYNC_COMPONENT_INDEX			= 1 << 4,
 };
 
+#ifndef FSYNC_COMPONENTS_PLATFORM_DEFAULT
+#define FSYNC_COMPONENTS_PLATFORM_DEFAULT FSYNC_COMPONENT_NONE
+#endif
+
 #define FSYNC_COMPONENTS_DEFAULT (FSYNC_COMPONENT_PACK | \
 				  FSYNC_COMPONENT_PACK_METADATA | \
-				  FSYNC_COMPONENT_COMMIT_GRAPH)
+				  FSYNC_COMPONENT_COMMIT_GRAPH | \
+				  FSYNC_COMPONENTS_PLATFORM_DEFAULT)
 
 #define FSYNC_COMPONENTS_OBJECTS (FSYNC_COMPONENT_LOOSE_OBJECT | \
 				  FSYNC_COMPONENT_PACK)

compat/mingw.h

@@ -332,6 +332,8 @@ int mingw_getpagesize(void);
 int win32_fsync_no_flush(int fd);
 #define fsync_no_flush win32_fsync_no_flush
 
+#define FSYNC_COMPONENTS_PLATFORM_DEFAULT FSYNC_COMPONENT_LOOSE_OBJECT
+
 struct rlimit {
 	unsigned int rlim_cur;
 };