rust-index: add fast-path for getting a list of all heads as nodes
This avoids a lot of back-and-forth between Python and Rust. We forgo adding
a fast-path in the `filteredchangelog` case yet. If it shows up in profiling,
we might add the variant with a filter.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}