git-svn: don't check for migrations/upgrades on commit-diff

Unlike other git-svn commands, commit-diff is intended to
operate without needing any additional metadata inside .git

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-svn.perl

@@ -147,7 +147,7 @@
 load_authors() if $_authors;
 load_all_refs() if $_branch_all_refs;
 svn_compat_check() unless $_use_lib;
-migration_check() unless $cmd =~ /^(?:init|rebuild|multi-init)$/;
+migration_check() unless $cmd =~ /^(?:init|rebuild|multi-init|commit-diff)$/;
 $cmd{$cmd}->[0]->(@ARGV);
 exit 0;