The general case does not need PKGDB_CREATE access

Reported by:	Matthew Seaman
Move write check into pkgcli_update()

Suggested by:	Matthew Seaman
pkg-shell.8: Be more specific on why this command should not be used and given hints on other options
install-info --delete should always be run in post-unexec
Revert "install-info --delete should always be run in post-unexec"
As a clean fix is coming to the ports tree

This reverts commit 9a055cd1f66e1d115b6c512918e606ed1d818e94.
Add reminder about pushing tags
Add a hint on how to support tar.xz in git-format-archive
Fix pkgconf handling