git difftool and git mergetool aren't returning errors when the tool has issues

For instance, if you set your diff/mergetool to meld and you don't have it installed:

git difftool

Viewing (1/1): 'blah'
Launch 'meld' [Y/n]? y
/home/ttanner/bin/meld[8]: /opt/swt/bin/meld: not found

echo $?

0

/home/ttanner/bin/meld

/home/ttanner/bin/meld[8]: /opt/swt/bin/meld: not found

echo $?

127

or

env DISPLAY=wibble git difftool

Viewing (1/1): blah'
Launch 'xxdiff' [Y/n]? y
xxdiff: cannot connect to X server wibble

echo $?

0

env DISPLAY=wibble xxdiff thisfile thatfile

xxdiff: cannot connect to X server wibble

echo $?

1
and this one (with DISPLAY unset because it was being run elsewhere)

git mergtool

Normal merge conflict for 'blah: 
{local}: modified file 
{remote}: modified file 
Could not find ':' in DISPLAY: yeah, right 
XIO: fatal IO error 73 (Connection reset by peer) on X server "server:66.0" 
after 0 requests (0 known processed) with 0 events remaining. 

echo $?

0
which last looked like a successful merge to a script, because it returned 0.