There are a handful of incorrect "linkgit:<page>[<section>]"
instances in our documentation set.
* Some have an extra colon after "linkgit:"; fix them by removing
the extra colon;
* Some refer to a page outside the Git suite, namely curl(1); fix
them by using the `curl(1)` that already appears on the same page
for the same purpose of referring the readers to its manual page.
* Some spell the name of the page incorrectly, e.g. "rev-list" when
they mean "git-rev-list"; fix them.
* Some list the manual section incorrectly; fix them to make sure
they match what is at the top of the target of the link.