Add flag to prevent .orig-files from being created

Author: bakgaard

gitconfig.txt

@@ -41,6 +41,8 @@
 	guitool = p4merge
 [merge]
 	tool = p4merge
+[mergetool]
+	keepBackup = false
 [mergetool "p4merge"]		
 	cmd = \"C:/Program Files/Git/mingw64/libexec/git-core/mergetools/p4merge.exe\" \"$BASE\" \"$LOCAL\" \"$REMOTE\" \"$MERGED\"
 	path = C:/Program Files/Git/mingw64/libexec/git-core/mergetools/p4merge.exe