BUG Report: v12.0.0 "git difftool -d" fails with "fatal: cannot create directory at '': No such file or directory"

I am building git from source using gcc 4.8.5 on 64 bit linux.

I am sorry the log info is not very helpful, please tell me how to get more information about what is going wrong and I will collect the info for you!

V2.12.0 Broken log ==============

Export GIT_TRACE=1
git difftool -d HEAD~ 
09:11:27.797674 git.c:371               trace: built-in: git 'difftool' '-d' 'HEAD~'
09:11:27.798255 run-command.c:369       trace: run_command: 'diff' '--raw' '--no-abbrev' '-z' 'HEAD~'
09:11:27.798484 exec_cmd.c:118          trace: exec: 'git' 'diff' '--raw' '--no-abbrev' '-z' 'HEAD~'
09:11:27.800156 git.c:371               trace: built-in: git 'diff' '--raw' '--no-abbrev' '-z' 'HEAD~'
fatal: cannot create directory at '': No such file or directory
	

Running make check gives fixed 0 success 14475 failed 0 broken 184 total 14804

Also broken in v2.12.0-rc0, v2.12.0-rc1 and v2.12.0-rc2 -----------------------------------------------------------------

V 2.11.1 works ===========