Why should you build novel length commit messages?
Commit messages should show WHY a change was made. Remember about the in-memory ordering caused by a default ordering in an ActiveRecord model that was removed after a while, but no one removed the in-memory ordering. https://vimeo.com/28AC0579162
Should you use git commit -m
No, the command line is not the place to write long commit messages explaining why a change was made.
What is better than git blame?
The pickaxe:
git log -S snippet_of_code
What is important in a commit message?
Explaining the WHY
NOT the what
Should you leave not valuable commits in history?
No, treat your commits as mutable. Use amend and rebase.