"sudo apt-get install foo-" causes removing foo package and everything depending on it

This is apparently a feature of apt.

From the manpage for the apt-get command ,

If a hyphen is appended to the package name (with no intervening space), the identified package will be removed if it is installed. Similarly a plus sign can be used to designate a package to install. These latter features may be used to override decisions made by apt-get's conflict resolution system.

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Simulating with an installed package and a hyphen appended to the end of the package gives me this output:

$ apt-get install -s retext-
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 package was automatically installed and is no longer required:
  retext-wpgen
Use 'apt-get autoremove' to remove it.
The following packages will be REMOVED:
  retext
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
Remv retext [3.1.3-1]

Similarly, with an uninstalled package and a plus sign appended to the end of the package, I get this output:

$ apt-get remove -s googlecl+
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:
  python-gdata
Suggested packages:
  python-gdata-doc
The following NEW packages will be installed:
  googlecl python-gdata
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Inst python-gdata (2.0.17-1 Ubuntu:12.10/quantal [all])
Inst googlecl (0.9.13-1.1 Ubuntu:12.10/quantal [all])
Conf python-gdata (2.0.17-1 Ubuntu:12.10/quantal [all])
Conf googlecl (0.9.13-1.1 Ubuntu:12.10/quantal [all])

Just tried this minus (or dash) sign after a package and yes , apt-get acting like remove.

Funny thing is I didn't know this function of apt-get . This minus sign is valid for every package . I tried with smplayer- with firefox- and always acting like remove. So the only thing I can think is that the dash sign at the end of a package considered by apt-get like a minus and install command converted to remove.

If you wanted to install everything about python3 , then you had to add an asterisk sign after this dash(minus) sign

sudo apt-get install python3-*

In the begin I thought this was just a conflict issue , but is not. Sometimes when you install some package and conflict with an other package then the already installed package will be removed due to new installed package , but this is not our situation here.

We've learned something useful today.

From the man-page of apt-get . To read the man-page via your terminal give man apt-get

If a hyphen (-) is appended to the package name (with no intervening space), the identified package will be removed if it is currently installed. Similarly a plus sign (+) can be used to designate a package to install. These latter features may be used to override decisions made by apt-get's conflict resolution system.

Eventually is not a new option or something weird , is just we don't read the man-pages carefully.