syntax: support `elif` clauses for alternative `if` syntax

In the alternative `if` syntax mode, support a specific `elif` keyword instead
of requiring an `else` branch followed by a disjunct `if` statement.

The advantage is that templates do not require error-prone redundant `endif`
keywords in else-if ladders.

After this change, the following example:

    {% if (...): %}
    One condition
    {% else if (...): %}
    Another condition
    {% else if (...): %}
    A third condition
    {% else %}
    Final condition
    {% endif; endif; endif %}

... can be simplified into:

    {% if (...): %}
    One condition
    {% elif (...): %}
    Another condition
    {% elif (...): %}
    A third condition
    {% else %}
    Final condition
    {% endif %}

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index de0b24e..8931aec 100644
--- a/eval.c
+++ b/eval.c
@@ -1562,6 +1562,7 @@ static struct json_object *(*fns[__T_MAX])(struct ut_state *, uint32_t) = {
 	[T_LBRACK]   = ut_execute_lbrack,
 	[T_LBRACE]   = ut_execute_object,
 	[T_IF]       = ut_execute_if,
+	[T_ELIF]     = ut_execute_if,
 	[T_QMARK]    = ut_execute_if,
 	[T_FOR]      = ut_execute_for,
 	[T_WHILE]    = ut_execute_while,