git-log.txt: add links to 'rev-list' and 'diff' docs
Add links to the documentation for `git rev-list` and `git diff`
instead of simply mentioning them, to make it easier for readers to reach
these documentation pages. Let's link to `git diff` as this is the
porcelain command, and the rest of the family (`diff-index`, `diff-tree` and
`diff-files`) are mentioned in the "Raw output format" section of the
`git diff` documentation.
Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>