Let's (try to) make Coverity's job easier

[nulltoken]

I've started to review Coverity findings. Some on them were raised because Coverity was unable to properly decipher Ensure.GitObjectIsNotNull() logic.

I've started to manually triage them as mark as False Positives.

Then, I eventually rollbacked my work and decided to simplify the code flow.

This PR also contains some minor fixes that I discovered while working on this.

[nulltoken]

Tweaked AppVeyor settings to schedule a daily run of Coverity analysis until all the issues are resolved.

[nulltoken]

/cc @whoisj

[whoisj]

I've been meaning to ask about this: is checking null all that needs to be done here or should some SafeHandle or IntPtr be checked as well?

[nulltoken]

Could you please open an issue about this?

[whoisj]

Generally 👍 as I'm a huge fan of simplicity. Only left a single comment, but action should be in a separate PR and not this one.

[nulltoken]

😿 That didn't help. Coverity results show that the analyzer didn't properly caught that a null GitObject could never be dereferenced once checked through Ensure.GitObjectIsNotNull().

I eventually had to tag some of the findings as false positives.

/cc @dakshesh-coverity