Stop implicitly manipulating `NO_COLOR`/`NOCOLOR`

Stop implicitly forcing `NO_COLOR` and `NOCOLOR` in ebuild environment.
This is undesired for several reasons:

1. It makes it impossible to control color for emerge output
   independently of command output, e.g. when one goes to a pty while
   the other goes to logs.

2. It makes it impossible to get color output in logs when running
   `emerge --jobs ...`.

3. Forcing `NO_COLOR=1` turns out to cause random test failures,
   and while fixing them is commendable, it is a pain for arch testing
   and it is currently blocking stabilization requests.

With the new approach, the color output in programs is consistent
between using ``--jobs`` or ``--quiet-build``, and not.  Therefore,
both cases generate uniform logs.  In order to obtain logs free of color
codes, one can either filter them via `ansifilter(1)` (as the manpages
already recommend) or explicitly set `NO_COLOR`.

Furthermore, one can combine color-free build output (for clean logs)
with colorful emerge output by using:

    NO_COLOR=true emerge --color y ...

Bug: https://bugs.gentoo.org/918515
Signed-off-by: Michał Górny <mgorny@gentoo.org>
Closes: https://github.com/gentoo/portage/pull/1188
Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index f1305744f..eb5eb4ab0 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,11 @@ Release notes take the form of the following optional categories:
 portage-3.0.56 (UNRELEASED)
 --------------
 
+Breaking changes:
+* ebuild: no longer implicitly set NOCOLOR and NO_COLOR when color output
+  is disabled for emerge itself.  In order to obtain color-free logs, please
+  either explicitly set NO_COLOR environment variable or use e.g. ansifilter.
+
 Features:
 * sync: git: Add sync-git-verify-max-age-days option.