Description of the new feature/enhancement

Users should be able to prevent the Windows Package Manager from updating a package (assumes the package doesn't have it's own auto-update).

winget pin <package> and the corollary winget unpin <package>.

This was mentioned by:

@megamorf #120 (comment)
@rodalpho #120 (comment)
@aetos382 #120 (comment)
@kmindi #120 (comment)

Proposed technical implementation details (optional)

There should also be a mechanism to display the packages (and the version) that have been "pinned". This might be a function of list or a function of pin. Additionally, if packages are known to self-update (like Visual Studio Code) an additional meta-data entry in the manifest could help users understand when they may not be able to pin a package.

Edit: Clarifying behavior for ambiguity suggested in other Issues.

Pinning should enable users to specify the exact version (likely the default case with no parameters).
It should also allow users to specify what portion of a version should be pinned so bug fixes could be applied, or even minor version bumps.

Note: the syntax below is just suggestive.

Assume the user has installed "Awesome App" version "1.2.3".

winget pin "Awesome App"
This would pin to version 1.2.3 and would not be upgraded when any newer version is released.

winget pin "Awesome App" --version 1.2
This would pin version to anything less than version 1.3. If version 1.2.4 were released this would be a valid upgrade.

winget pin "Awesome App" --version 1
This would pin the version to anything less than version 2. If version 1.2.4 were released this would be a valid upgrade. If version 1.3.0 were released this would also be a valid upgrade.

Additional example per @brainz80

E.g. Having nodejs-lts version 12.1.1 installed and running winget pin --all nodejs-lts --version 12.x should make it so that when later winget upgrade --all is ran it'd check if there is a update available for nodejs-lts what matches 12.x - if the latest update is e.g 16.1.1, but there is also a 12.1.2 it'd update nodejs-lts to that version.