It's actually not checking, it's resolving. Instead of ...
get_commit($symbol)
... (with $symbol = 'HEAD' for instance), you do (pseudocode):
$hash = get_hash($symbol, 'commit'); # 'commit' to resolve tags
check that $hash is defined
get_commit($hash)
(And get_commit won't even accept anything but 40-byte hashes.) This is
for two reasons:
1. Caching: Resolving symbols first gives you some (very few) cache
entries that need to be expired (namely, get_hash results for symbols
that are not SHA1 hashes already), but most cache entries (like the
get_commit) are infinitely valid.
2. Besides being a little more straightforward to implement, it ensures
that you have well-defined failure points. IOW, first you resolve the
symbols you're getting from the user and check them for existence (and
correct type). From then on, any hashes you pass around are guaranteed
to be valid, so failures indicate that something serious went wrong.
Apart from making things easier for the developer by reminding them of
the points where they *need* to check for errors, it means that you can
very easily check the error-handling code for completeness (by only
reading the first few lines that resolve symbols).
Will do in the next 2 days after some cleanup.
It makes things better to read for sure, and it means that you can have
a plain API without caching, and implement the caching layer as a
subclass (which overrides the methods with cacheable results).
-- Lea
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