declare local constants instead of using magic values and comments

avoid using abbreviations that look like spelling errors

improve some comments and docstrings, fixing issues found when spell checking

delete some dead comments and docstrings

fix wording and not-completely-trivial spelling errors and bad docstrings

fix trivial spelling errors

strip: fix revset usage (issue3604) The `repair` code builds a giant revset query instead of using the "%lr" idiom. It is inefficient and crash when the number of stripped changeset is too big. This changeset replaces the bad code by a better revset usage.