gvfs: add the feature to skip validation of the index' SHA-1

This takes a substantial amount of time, and if the user is reasonably
sure that the files' integrity is not compromised, that time can be saved.

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

Documentation/config.txt

@@ -920,7 +920,15 @@ This setting defaults to "refs/notes/commits", and it can be overridden by
 the `GIT_NOTES_REF` environment variable.  See linkgit:git-notes[1].
 
 core.gvfs::
-	Enable the features needed for GVFS.
+	Enable the features needed for GVFS.  This value can be set to true
+	to indicate all features should be turned on or the bit values listed
+	below can be used to turn on specific features.
++
+--
+	GVFS_SKIP_SHA_ON_INDEX_READ::
+		Bit value 1
+		Disables the calculation and validation of the sha when reading the index
+--
 
 core.sparseCheckout::
 	Enable "sparse checkout" feature. See section "Sparse checkout" in

gvfs.h

@@ -9,6 +9,12 @@
  * used for GVFS functionality
  */
 
+
+/*
+ * The list of bits in the core_gvfs setting
+ */
+#define GVFS_SKIP_SHA_ON_INDEX                      (1 << 0)
+
 static inline int gvfs_config_is_set(int mask) {
 	return (core_gvfs & mask) == mask;
 }

read-cache.c

@@ -20,6 +20,7 @@
 #include "split-index.h"
 #include "utf8.h"
 #include "fsmonitor.h"
+#include "gvfs.h"
 
 /* Mask for the name length in ce_flags in the on-disk index */
 
@@ -1586,6 +1587,14 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size)
 	if (!verify_index_checksum)
 		return 0;
 
+	/*
+	Since gitmodules_config runs this code
+	and is called before git_config(git_default_config, ...)
+	the config values are not loaded and has to be retrieved directly here.
+	*/
+	if (gvfs_config_load_and_is_set(GVFS_SKIP_SHA_ON_INDEX))
+		return 0;
+
 	the_hash_algo->init_fn(&c);
 	the_hash_algo->update_fn(&c, hdr, size - the_hash_algo->rawsz);
 	the_hash_algo->final_fn(hash, &c);
@@ -1992,7 +2001,9 @@ static int ce_write_flush(git_hash_ctx *context, int fd)
 {
 	unsigned int buffered = write_buffer_len;
 	if (buffered) {
-		the_hash_algo->update_fn(context, write_buffer, buffered);
+		if (!gvfs_config_is_set(GVFS_SKIP_SHA_ON_INDEX))
+			the_hash_algo->update_fn(context, write_buffer,
+						 buffered);
 		if (write_in_full(fd, write_buffer, buffered) < 0)
 			return -1;
 		write_buffer_len = 0;
@@ -2037,7 +2048,8 @@ static int ce_flush(git_hash_ctx *context, int fd, unsigned char *hash)
 
 	if (left) {
 		write_buffer_len = 0;
-		the_hash_algo->update_fn(context, write_buffer, left);
+		if (!gvfs_config_is_set(GVFS_SKIP_SHA_ON_INDEX))
+			the_hash_algo->update_fn(context, write_buffer, left);
 	}
 
 	/* Flush first if not enough space for hash signature */
@@ -2048,7 +2060,8 @@ static int ce_flush(git_hash_ctx *context, int fd, unsigned char *hash)
 	}
 
 	/* Append the hash signature at the end */
-	the_hash_algo->final_fn(write_buffer + left, context);
+	if (!gvfs_config_is_set(GVFS_SKIP_SHA_ON_INDEX))
+		the_hash_algo->final_fn(write_buffer + left, context);
 	hashcpy(hash, write_buffer + left);
 	left += the_hash_algo->rawsz;
 	return (write_in_full(fd, write_buffer, left) < 0) ? -1 : 0;

t/t1015-read-tree-skip-sha-on-read.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+test_description='check that read-tree works with core.gvfs config value'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-read-tree.sh
+
+test_expect_success setup '
+	echo one >a &&
+	git add a &&
+	git commit -m initial
+'
+test_expect_success 'read-tree without core.gvsf' '
+	read_tree_u_must_succeed -m -u HEAD
+'
+
+test_expect_success 'read-tree with core.gvfs set to 1' '
+	git config core.gvfs 1 &&
+	read_tree_u_must_succeed -m -u HEAD
+'
+
+test_done