Merge branch 'lt/default-abbrev'

* lt/default-abbrev:
  Rename core.abbrevlength back to core.abbrev
  Make the default abbrev length configurable

environment.c

@@ -15,6 +15,7 @@ int user_ident_explicitly_given;
 int trust_executable_bit = 1;
 int trust_ctime = 1;
 int has_symlinks = 1;
+int minimum_abbrev = 4, default_abbrev = 7;
 int ignore_case;
 int assume_unchanged;
 int prefer_symlink_refs;