This patch continues the effort that is already applied to
`git commit`, `git reset`, `git checkout` etc.
1) Changed outdated descriptions to mention pathspec instead.
2) Added reference to 'linkgit:gitglossary[7]'.
3) Removed content that merely repeated gitglossary.
4) Merged the remainder of "discussion" into `<patchspec>`.
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>