Merge branch 'jk/no-optional-locks'

Some commands (most notably "git status") makes an opportunistic
update when performing a read-only operation to help optimize later
operations in the same repository.  The new "--no-optional-locks"
option can be passed to Git to disable them.

* jk/no-optional-locks:
  git: add --no-optional-locks option

cache.h

@@ -444,6 +444,7 @@ static inline enum object_type object_type(unsigned int mode)
 #define GIT_NOGLOB_PATHSPECS_ENVIRONMENT "GIT_NOGLOB_PATHSPECS"
 #define GIT_ICASE_PATHSPECS_ENVIRONMENT "GIT_ICASE_PATHSPECS"
 #define GIT_QUARANTINE_ENVIRONMENT "GIT_QUARANTINE_PATH"
+#define GIT_OPTIONAL_LOCKS_ENVIRONMENT "GIT_OPTIONAL_LOCKS"
 
 /*
  * This environment variable is expected to contain a boolean indicating
@@ -783,6 +784,11 @@ extern int protect_ntfs;
  */
 extern int ref_paranoia;
 
+/*
+ * Returns the boolean value of $GIT_OPTIONAL_LOCKS (or the default value).
+ */
+int use_optional_locks(void);
+
 /*
  * The character that begins a commented line in user-editable file
  * that is subject to stripspace.