Added a --target parameter to uninstall to allow uninstalling from custom folders

[mitsuhiko]

Essentially what it says on the tin. It adds a --target parameter that allows pip uninstall to uninstall from a specific folder instead of the site packages.

This is necessary for pips installed into a virtualenv as otherwise the virtualenv containment check prevents a deinstallation. It also is a bit safer because it will not uninstall from outside.

[Ivoz]

as otherwise the virtualenv containment check prevents a deinstallation

Can you explain what you exactly mean by this? Or otherwise, perhaps give specific detail of the practical use case that motivates this PR? You want to uninstall things outside a virtualenv with a pip inside a virtualenv?

[mitsuhiko]

Currently there is no way to uninstall something installed via --target unless you use a globally installed pip because of the restrictions of pip in virtualenvs. That restriction makes sense and I do not advocate for removing it and instead have a separate flag on uninstall that can uninstall from a specific folder.

As of why this is useful: I want to use pip for plugin installations and install plugins into a local folder that only by the application is added to the pythonpath.

[webmaven]

On a related note, right now installations to a target folder have multiple problems ( #1489, #1636, #1710, #1818, #1833).

[webmaven]

@dstufft this looks like it could use some attention too.

[webmaven]

@pfmoore @jonparrott This looks like a good next candidate for merging, if the conflicts are resolved.

[msabramo]

@mitsuhiko: Want to update this?

[dstufft]

Accidentally closed this, reopening. Sorry!

[BrownTruck]

Hello!

As part of an effort to ease the contribution process and adopt a more standard workflow pip has switched to doing development on the master branch. However, this Pull Request was made against the develop branch so it will need to be resubmitted against master. Unfortunately, this pull request does not cleanly merge against the current master branch.

If you do nothing, this Pull Request will be automatically closed by @BrownTruck since it cannot be merged.

If this pull request is still valid, please rebase it against master (or merge master into it) and resubmit it against the master branch, closing and referencing the original Pull Request.

If you choose to rebase/merge and resubmit this Pull Request, here is an example message that you can copy and paste:

Essentially what it says on the tin.  It adds a --target parameter that allows pip uninstall to uninstall from a specific folder instead of the site packages.

This is necessary for pips installed into a virtualenv as otherwise the virtualenv containment check prevents a deinstallation.  It also is a bit safer because it will not uninstall from outside.

---

*This was migrated from pypa/pip#1912 to reparent it to the ``master`` branch. Please see original pull request for any previous discussion.*

[webmaven]

@mitsuhiko, can you reparent this PR as requested?

[BrownTruck]

This Pull Request was closed because it cannot be automatically reparented to the master branch and it appears to have bit rotted.

Please feel free to re-open it or re-submit it if it is still valid and you have rebased it onto master or merged master into it.

[webmaven]

:-(