Feat: Option to yield immediately when watcher starts

[FelixFourcolor]

I think it's a common pattern to first run a function unconditionally, then re-run every time a file changes (e.g. a live web server that refreshes when code changes).

You can do this:

foo()
for _ in watchfiles.watch(file):
    foo()

The issue with this is, changes that happen during the first run won't be registered. Currently there isn't a nice way to express this pattern.

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Suggestion: Add this option

def watch(..., yield_on_start: bool):
    with RustNotify(...):
        if yield_on_start:
            yield set()
        while True:
            ...  # remaining code