> Where do you look first?
Git commit will generally explain why it was done. The task it references may or may not explain the decision process that lead to it. Usually not.
It's rarely related to code, more often a business decision due to some obscure reason/desire which may or may not provide any actual value.
> Git commit will generally explain why it was done.
Sometimes, not generally. A lot of people are bad at commit messages, and commits migrated from older tools may be unusably terse because those tools didn't support multi-line commit messages well.