`where` template function's internal condition check function always
returns `false` when a target value doesn't exist or it's nil value but
this behavior makes it difficult to filter values which doesn't have a
particular parameter.
To solve it, this adds nil value comparison to the function.
`where Values ".Param.key" nil` like clause can be used for the case
above.
Only "=", "==", "eq", "!=", "<>", "ne" operators are allowed to be used
with `nil`. If an other operator is passed with `nil`, the condition
check function returns `false` like before.
Fix#1232
Where `first` will return the first N items of a rangeable list,
`after` will return all items after the Nth item.
This allows the user to do something with the first N items and
something different with the remaining items after N.
`substr` template function takes one or two range arguments. Both
arguments must be int type values but if it is used with a calclation
function e.g. `add`, `len` etc, it causes a wrong type error.
This fixes the issue to allow the function to take other integer type
variant like `int64` etc.
This also includes a small fix on no range argument case.
Fix#1190
`where` tpl function doesn't support `time.Time` type so if people want
to compare such values, it's required that these values are converted
into `int` and compare them.
This improves it. If `time.Time` values are passed to `where`, it
converts them into `int` internally, compares them and returns the
result.
See also
http://discuss.gohugo.io/t/future-posts-and-past-posts/1229/3
