How to check the version before installing a package using apt-get?

Question

OK, I found it.

apt-cache policy <package name> will show the version details.

It also shows which version is currently installed and which versions are available to install.

For example, apt-cache policy hylafax+

apt-cache policy <package-name>

$ apt-cache policy redis-server
redis-server:
  Installed: (none)
  Candidate: 2:2.8.4-2
  Version table:
     2:2.8.4-2 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages

apt-get install -s <package-name>

$ apt-get install -s redis-server
NOTE: This is only a simulation!
      apt-get needs root privileges for real execution.
      Keep also in mind that locking is deactivated,
      so don't depend on the relevance to the real current situation!
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libjemalloc1 redis-tools
The following NEW packages will be installed:
  libjemalloc1 redis-server redis-tools
0 upgraded, 3 newly installed, 0 to remove and 3 not upgraded.
Inst libjemalloc1 (3.5.1-2 Ubuntu:14.04/trusty [amd64])
Inst redis-tools (2:2.8.4-2 Ubuntu:14.04/trusty [amd64])
Inst redis-server (2:2.8.4-2 Ubuntu:14.04/trusty [amd64])
Conf libjemalloc1 (3.5.1-2 Ubuntu:14.04/trusty [amd64])
Conf redis-tools (2:2.8.4-2 Ubuntu:14.04/trusty [amd64])
Conf redis-server (2:2.8.4-2 Ubuntu:14.04/trusty [amd64])

apt-cache show <package-name>

$ apt-cache show redis-server
Package: redis-server
Priority: optional
Section: universe/misc
Installed-Size: 744
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Chris Lamb <[email protected]>
Architecture: amd64
Source: redis
Version: 2:2.8.4-2
Depends: libc6 (>= 2.14), libjemalloc1 (>= 2.1.1), redis-tools (= 2:2.8.4-2), adduser
Filename: pool/universe/r/redis/redis-server_2.8.4-2_amd64.deb
Size: 267446
MD5sum: 066f3ce93331b876b691df69d11b7e36
SHA1: f7ffbf228cc10aa6ff23ecc16f8c744928d7782e
SHA256: 2d273574f134dc0d8d10d41b5eab54114dfcf8b716bad4e6d04ad8452fe1627d
Description-en: Persistent key-value database with network interface
 Redis is a key-value database in a similar vein to memcache but the dataset
 is non-volatile. Redis additionally provides native support for atomically
 manipulating and querying data structures such as lists and sets.
 .
 The dataset is stored entirely in memory and periodically flushed to disk.
Description-md5: 9160ed1405585ab844f8750a9305d33f
Homepage: http://redis.io/
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubunt

dpkg -l <package-name>

$ dpkg -l nginx
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                     Version                   Architecture              Description
+++-========================================-=========================-=========================-=====================================================================================
ii  nginx                                    1.6.2-1~trusty            amd64                     high performance web server

apt policy <package>

for short

Linux Mint, Debian 9, Ubuntu 16.04 and older:

Short info:

apt policy <package_name>

Detailed info (With Description and Depends):

apt show <package_name>

The following might work well enough:

aptitude versions ^hylafax+

See more in aptitude(8)

on debian :

apt list --upgradable

gives the list with package, version to be upgraded, and actual version of the package.

result :

base-files/stable 8+deb8u8 amd64 [upgradable from: 8+deb8u7]
bind9-host/stable 1:9.9.5.dfsg-9+deb8u11 amd64 [upgradable from: 1:9.9.5.dfsg-9+deb8u9]
ca-certificates/stable 20141019+deb8u3 all [upgradable from: 20141019+deb8u2]
certbot/jessie-backports 0.10.2-1~bpo8+1 all [upgradable from: 0.8.1-2~bpo8+1]
dnsutils/stable 1:9.9.5.dfsg-9+deb8u11 amd64 [upgradable from: 1:9.9.5.dfsg-9+deb8u9]