One more time.. Clean up git-merge-one-file-script

This uses git-checkout-file to make sure that the full pathname is
created, instead of the script having to verify it by hand.  Also,
simplify the 3-way merge case by just writing to the right file and
setting the initial index contents early.

git-merge-one-file-script

@@ -16,29 +16,11 @@
 # been handled already by git-read-tree, but that one doesn't
 # do any merges that might change the tree layout.
 
-verify_path() {
-    file="$1"
-    dir=`dirname "$file"` &&
-    mkdir -p "$dir" &&
-    rm -f -- "$file" &&
-    : >"$file"
-}
-
 case "${1:-.}${2:-.}${3:-.}" in
 #
-# Deleted in both.
-#
-"$1..")
-	echo "WARNING: $4 is removed in both branches."
-	echo "WARNING: This is a potential rename conflict."
-	rm -f -- "$4" &&
-		exec git-update-cache --remove -- "$4"
-	;;
-
-#
-# Deleted in one and unchanged in the other.
+# Deleted in both or deleted in one and unchanged in the other
 #
-"$1.$1" | "$1$1.")
+"$1.." | "$1.$1" | "$1$1.")
 	echo "Removing $4"
 	rm -f -- "$4" &&
 		exec git-update-cache --remove -- "$4"
@@ -48,12 +30,9 @@ case "${1:-.}${2:-.}${3:-.}" in
 # Added in one.
 #
 ".$2." | "..$3" )
-	case "$6$7" in *7??) mode=+x;; *) mode=-x;; esac
-	echo "Adding $4 with perm $mode."
-	verify_path "$4" &&
-		git-cat-file blob "$2$3" >"$4" &&
-		chmod $mode -- "$4" &&
-		exec git-update-cache --add -- "$4"
+	echo "Adding $4"
+	git-update-cache --add --cacheinfo "$6$7" "$2$3" "$4" &&
+		exec git-checkout-cache -u -f -- "$4"
 	;;
 
 #
@@ -65,12 +44,9 @@ case "${1:-.}${2:-.}${3:-.}" in
 		echo "ERROR: but permissions conflict $6->$7."
 		exit 1
 	fi
-	case "$6" in *7??) mode=+x;; *) mode=-x;; esac
-	echo "Adding $4 with perm $mode"
-	verify_path "$4" &&
-		git-cat-file blob "$2" >"$4" &&
-		chmod $mode -- "$4" &&
-		exec git-update-cache --add -- "$4"
+	echo "Adding $4"
+	git-update-cache --add --cacheinfo "$6" "$2" "$4" &&
+		exec git-checkout-cache -u -f -- "$4"
 	;;
 
 #
@@ -79,29 +55,26 @@ case "${1:-.}${2:-.}${3:-.}" in
 "$1$2$3")
 	echo "Auto-merging $4."
 	orig=`git-unpack-file $1`
-	src1=`git-unpack-file $2`
 	src2=`git-unpack-file $3`
 
-	verify_path "$4" &&
-		merge -p "$src1" "$orig" "$src2" > "$4"
+	# We reset the index to the first branch, making
+	# git-diff-file useful
+	git-update-cache --add --cacheinfo "$6" "$2" "$4" 
+		git-checkout-cache -u -f -- "$4" &&
+		merge "$4" "$orig" "$src2"
 	ret=$?
-	rm -f -- "$orig" "$src1" "$src2"
+	rm -f -- "$orig" "$src2"
 
 	if [ "$6" != "$7" ]; then
 		echo "ERROR: Permissions conflict: $5->$6,$7."
 		ret=1
 	fi
-	case "$6" in *7??) mode=+x;; *) mode=-x;; esac
-	chmod "$mode" "$4"
 
 	if [ $ret -ne 0 ]; then
-		# Reset the index to the first branch, making
-		# git-diff-file useful
-		git-update-cache --add --cacheinfo "$6" "$2" "$4"
 		echo "ERROR: Merge conflict in $4."
 		exit 1
 	fi
-	exec git-update-cache --add -- "$4"
+	exec git-update-cache -- "$4"
 	;;
 
 *)