Hello, everyone.

I'd like to start a series of mails dedicated to features proposed for
including in EAPI 8.  For a start, I'd like to discuss the topic of
selective fetch restriction [1].  It has been discussed at least in 2013
[2], and since it's finally got chance to be included, I think it's
worthwhile to rehash it.


The problem
===========
Fetch/mirror restriction as of now can only be applied to all distfiles
at once.  This causes problems in the (rather rare) case when we'd like
to add some additional files to SRC_URI that do not require the big
restriction.  As a result, the user is forced to manually fetch all
the files even if only one truly requires it.


Proposed solution
=================
The current proposal is based on extending the current URI syntax to
permit excluding individual files from the restriction.  The idea is to
prepend 'fetch+' to protocol to undo fetch restriction, or to prepend
'mirror+' to undo fetch & mirror restrictions.

Example 1: removing mirror restriction from files

RESTRICT="mirror"
SRC_URI="https://example.com/you-cant-mirror-this.tar.bz2
  mirror+https://example.com/but-you-can-mirror-this.tar.gz"

Example 2: removing fetch & mirror restriction from files

RESTRICT="fetch"
SRC_URI="https://example.com/you-cant-fetch-this.zip
  mirror+https://example.com/but-you-can-mirror-this.tar.gz"

Example 3: removing fetch restriction while leaving mirror restriction

RESTRICT="fetch"
SRC_URI="https://example.com/you-cant-fetch-this.zip
   fetch+https://example.com/you-cant-mirror-this.tar.bz2"


Comments
========
WDYT?


References
==========
[1] https://bugs.gentoo.org/371413
[2] https://archives.gentoo.org/gentoo-dev/message/b0823618d5d3cc61bbed1e88dc2f144d

-- 
Best regards,
Michał Górny