[PATCH v4 2/4] fsck: force core.checksumindex=1

[git@jeffhostetler.com]

From: Jeff Hostetler <jeffhost@microsoft.com>

Teach fsck to override core.checksumindex and always verify
the index checksum when reading the index.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 builtin/fsck.c |  1 +
 cache.h        |  7 +++++++
 read-cache.c   | 20 +++++++++++++-------
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/builtin/fsck.c b/builtin/fsck.c
index 1a5cacc..6913233 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -771,6 +771,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 	}
 
 	if (keep_cache_objects) {
+		force_core_checksum_index = 1;
 		read_cache();
 		for (i = 0; i < active_nr; i++) {
 			unsigned int mode;
diff --git a/cache.h b/cache.h
index 80b6372..3ebda0a 100644
--- a/cache.h
+++ b/cache.h
@@ -685,6 +685,13 @@ extern void update_index_if_able(struct index_state *, struct lock_file *);
 extern int hold_locked_index(struct lock_file *, int);
 extern void set_alternate_index_output(const char *);
 
+/*
+ * Override "core.checksumindex" config settings.  Allows commands
+ * like "fsck" to force it without altering on-disk settings in case
+ * routines call die() before it can be reset.
+ */
+extern int force_core_checksum_index;
+
 /* Environment bits from configuration mechanism */
 extern int trust_executable_bit;
 extern int trust_ctime;
diff --git a/read-cache.c b/read-cache.c
index dd64cde..36fdc2a 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1371,6 +1371,8 @@ struct ondisk_cache_entry_extended {
 			    ondisk_cache_entry_extended_size(ce_namelen(ce)) : \
 			    ondisk_cache_entry_size(ce_namelen(ce)))
 
+int force_core_checksum_index;
+
 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 {
 	git_SHA_CTX c;
@@ -1384,13 +1386,17 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size)
 	if (hdr_version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < hdr_version)
 		return error("bad index version %d", hdr_version);
 
-	/*
-	 * Since we run very early in command startup, git_config()
-	 * may not have been called yet and the various "core_*"
-	 * global variables haven't been set.  So look it up
-	 * explicitly.
-	 */
-	git_config_get_bool("core.checksumindex", &do_checksum);
+	if (force_core_checksum_index)
+		do_checksum = 1;
+	else {
+		/*
+		 * Since we run very early in command startup, git_config()
+		 * may not have been called yet and the various "core_*"
+		 * global variables haven't been set.  So look it up
+		 * explicitly.
+		 */
+		git_config_get_bool("core.checksumindex", &do_checksum);
+	}
 	if (!do_checksum)
 		return 0;
 
-- 
2.9.3