[BUG] Veryfing signatures in git log fails when language is not english

Hi,

any functionality that depends on exact exit msg of program
 can potentially fail because of that
ᛯ export |grep LANG
declare -x LANG="pl_PL.UTF-8"

ᛯ ~/src/os/git/git log --format="%G? %h" |head -2 
 0d19377
 5b9d7f8

ᛯ unset LANG ᛯ ~/src/os/git/git log --format="%G? %h" |head -2 G 0d19377 G 5b9d7f8

tested against maint (d32805d) and master (5bf72ed)

maybe git should set up some output-changing variables before calling external programs? I think setting LC_ALL=C should be enougth.