[Nit] Lots of enumerated type warnings

So here a bit of a nit or nano-quibble that I have. Call it my "warnings OCD" if you want. I'm seeing an increase in the enumerated type warnings coming from my use of the c99 compiler for compiling git over time (loads more for 2.16.0 compared to 2.3.7 when I took it on). What is the general feeling on these? I would be willing do static casts rather than see the warnings, mostly because I advocate in public that warnings are actually future potential errors, so clean compiles are better. I don't see this conflicting with anything in gcc. Is there a desire/need to clean up this stuff? I can take a stab at gradually cleaning this up when $DAYJOB and #FAMILY don't conflict.

Although, given the choice, I'd rather look into that whole --via concept from a different thread ;-)

Cheers, Randall

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