Recover the complicated situation after my bad merge

I made a mistake merge.  Reverting it in c778945806 undid the state
on master, but now I realize it crippled the git merge mechanism.
As the merge contained a mix of commits from `master..staging-next`
and other commits from `staging-next..staging`, it got the
`staging-next` branch into a state that was difficult to recover.

I reconstructed the "desired" state of staging-next tree by:
 - checking out the last commit of the problematic range: 4effe769e2
 - `git rebase -i --preserve-merges a8a018ddc0` - dropping the mistaken
   merge commit and its revert from that range (while keeping
   reapplication from 4effe769e2)
 - merging the last unaffected staging-next commit (803ca85c20)
 - fortunately no other commits have been pushed to staging-next yet
 - applying a diff on staging-next to get it into that state

pkgs/development/tools/build-managers/meson/boost-Do-not-add-system-paths-on-nix.patch

@@ -0,0 +1,40 @@
+From 536108b10271f2f42d41c7d9ddb4ce2ea1851f4f Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Niklas=20Hamb=C3=BCchen?= <mail@nh2.me>
+Date: Sat, 17 Oct 2020 19:27:08 +0200
+Subject: [PATCH] boost: Do not add system paths on nix
+
+---
+ mesonbuild/dependencies/boost.py | 17 +----------------
+ 1 file changed, 1 insertion(+), 16 deletions(-)
+
+diff --git a/mesonbuild/dependencies/boost.py b/mesonbuild/dependencies/boost.py
+index 907c0c275..ecaf11b18 100644
+--- a/mesonbuild/dependencies/boost.py
++++ b/mesonbuild/dependencies/boost.py
+@@ -643,22 +643,7 @@ class BoostDependency(ExternalDependency):
+             roots += [x for x in candidates if x.name.lower().startswith('boost') and x.is_dir()]
+         else:
+             tmp = []  # type: T.List[Path]
+-
+-            # Homebrew
+-            brew_boost = Path('/usr/local/Cellar/boost')
+-            if brew_boost.is_dir():
+-                tmp += [x for x in brew_boost.iterdir()]
+-
+-            # Add some default system paths
+-            tmp += [Path('/opt/local')]
+-            tmp += [Path('/usr/local/opt/boost')]
+-            tmp += [Path('/usr/local')]
+-            tmp += [Path('/usr')]
+-
+-            # Cleanup paths
+-            tmp = [x for x in tmp if x.is_dir()]
+-            tmp = [x.resolve() for x in tmp]
+-            roots += tmp
++            # Do not add any non-explicit paths on nix
+ 
+         return roots
+ 
+-- 
+2.25.4
+