[gentoo-dev] alternatives.eclass

[Alastair Tse]

Hi All,

I've written a helper function in an eclass form which maybe useful to
some of you who maintain SLOT'ed packages. I'm trying to solicit any
arguments for or against committing this to the tree.

Essentially, some slotted packages require a symlink to link to the
latest version of an executable or library. For instance, dev-util/guile
and dev-lang/python. However, because it is not guaranteed that a user
will merge a package in the natural version order, it is possible that a
symlink may not point to the latest version.

To illustrate this example further, consider this:

emerge =dev-lang/python-2.2.3
# this will create /usr/bin/python -> /usr/bin/python2.2
emerge =dev-lang/python-2.3.2
# this will create /usr/bin/python -> /usr/bin/python2.3
emerge =dev-lang/python-2.2.3-r1
# this will create /usr/bin/python -> /usr/bin/python2.2

Given that python is slotted (2.2 and 2.3), this means /usr/bin/python
no longer points to the latest version even though it should and the
user would expect it to.

Therefore, this simple script will iterate through a sorted list of
choices to symlink and choose the first one that exists. This would be
useful to putting into pkg_postinst() and pkg_postrm() to make sure the
symlinks are correct.

The details are in the eclass itself that can be found at:

http://dev.gentoo.org/~liquidx/files/alternatives.eclass

And an example of it's use can be found in:

http://dev.gentoo.org/~liquidx/files/python-2.2.3-r2.ebuild

Cheers,
-- 
Alastair 'liquidx' Tse
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