gvfs: add the feature that blobs may be missing

Signed-off-by: Kevin Willford <kewillf@microsoft.com>

Documentation/config/core.txt

@@ -737,6 +737,10 @@ core.gvfs::
 	GVFS_SKIP_SHA_ON_INDEX::
 		Bit value 1
 		Disables the calculation of the sha when writing the index
+	GVFS_MISSING_OK::
+		Bit value 4
+		Normally git write-tree ensures that the objects referenced by the
+		directory exist in the object database. This option disables this check.
 --
 
 core.sparseCheckout::

cache-tree.c

@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "gvfs.h"
 #include "lockfile.h"
 #include "tree.h"
 #include "tree-walk.h"
@@ -252,7 +253,8 @@ static int update_one(struct cache_tree *it,
 		      int flags)
 {
 	struct strbuf buffer;
-	int missing_ok = flags & WRITE_TREE_MISSING_OK;
+	int missing_ok = gvfs_config_is_set(GVFS_MISSING_OK) ?
+		WRITE_TREE_MISSING_OK : (flags & WRITE_TREE_MISSING_OK);
 	int dryrun = flags & WRITE_TREE_DRY_RUN;
 	int repair = flags & WRITE_TREE_REPAIR;
 	int to_invalidate = 0;

gvfs.h

@@ -14,6 +14,7 @@
  * The list of bits in the core_gvfs setting
  */
 #define GVFS_SKIP_SHA_ON_INDEX                      (1 << 0)
+#define GVFS_MISSING_OK                             (1 << 2)
 
 static inline int gvfs_config_is_set(int mask) {
 	return (core_gvfs & mask) == mask;

t/t0000-basic.sh

@@ -1105,6 +1105,11 @@ test_expect_success 'writing this tree with --missing-ok' '
 	git write-tree --missing-ok
 '
 
+test_expect_success 'writing this tree with missing ok config value' '
+	git config core.gvfs 4 &&
+	git write-tree
+'
+
 
 ################################################################
 test_expect_success 'git read-tree followed by write-tree should be idempotent' '