merge-octopus: use die shell function from git-sh-setup.sh

Source git-sh-setup in order to use die shell function from
git-sh-setup.sh library instead of using the one defined in
git-merge-octopus.sh. Remove the former die function.

Signed-off-by: Vasco Almeida <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: vascool

git-merge-octopus.sh

@@ -5,16 +5,12 @@
 # Resolve two or more trees.
 #
 
+. git-sh-setup
 . git-sh-i18n
 
 LF='
 '
 
-die () {
-    echo >&2 "$*"
-    exit 1
-}
-
 # The first parameters up to -- are merge bases; the rest are heads.
 bases= head= remotes= sep_seen=
 for arg