git-revert: Fix die before git-sh-setup defines it.
git-revert: Fix die before git-sh-setup defines it.

The code previously checked it's own name and called 'die' upon
an error.  However 'die' was not yet defined because git-sh-setup
had not been sourced yet.  Instead simply write the error message
to stderr and exit with an error as was originally desired.

Signed-off-by: Bob Proulx <48181acd22b3edaebc8a447868a7df7ce629920a@proulx.com>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git