git-diff: unable to turn off diff.autorefreshindex with command line switch

Hello,

I am seeing unexpected behaviour on my system with git-diff and stat-only changes: diff.autorefreshindex=0 only works when in a repo's config (./.git/config); it doesn't work via a -c switch.  Conversely -c diff.autorefreshindex=1 does indeed override a 0 setting in the repo's config.

# First I remove all my normal configs. $ mv ~/.git* ~/stuff/

# Now some setup.
$ mkdir foo && cd foo
$ git init
$ echo 123 > README
$ git commit -am 'initial'
[master (root-commit) 92e793c] initial
 ...[stuff about name and email address being auto-configured]...
 1 file changed, 1 insertion(+)
 create mode 100644 README
$ touch README

# Now the strange behaviour: no output from the next command $ git -c diff.autorefreshindex=0 diff --raw -- README

$ cat .git/config
[core]
	repositoryformatversion = 0
	filemode = true
	bare = false
	logallrefupdates = true
	ignorecase = true
	precomposeunicode = true

$ echo -e "[diff]\n autorefreshindex = 0" >> .git/config $ touch README

# Next command works as expected. $ git diff --raw -- README :100644 100644 190a180... 0000000... M README

# Next command produces no output as expected $ git -c diff.autorefreshindex=1 diff --raw -- README

I get this with both git v2.6.4 and v2.7.0 on my OS X 10.11.2.  I tried it on another system (Ubuntu 12.04 LTS, git 1.7.9.5) and everything worked as expected.  Somebody else tried it on their OS X 10.11.2 (as well as 10.10.something) with git 2.5.4 and everything worked as expected.

Any help would be much appreciated.  Thanks in advance!

Yours, Andrew Stewart