Refine a bit the decentralized merging process.

We make GitHub assign only principal maintainers as reviewers. This
reduces the level of noise (PRs with 10 code owners), and makes it easy
for the assignee to check if all reviews have been completed (all
reviewers in the list have to approve the PR, which was not the case
before if two reviewers were assigned for the same component).

This change means that when a principal maintainer submits a patch
touching the component they own, they should ask a review from the
secondary maintainer.

1 files changed, 256 insertions, 85 deletions

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index b64212dff..9a33abad6 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -1,124 +1,295 @@
 # This file describes the maintainers for the main components. See
 # `dev/doc/MERGING.md`.
 
-# component-path  principal-maintainer secondary-maintainer
+########## GitHub metadata, including this file ##########
 
-# GitHub metadata, including this file
-/.github/         @maximedenes @Zimmi48
+/.github/         @maximedenes
+# Secondary maintainer @Zimmi48
 
-# CI infrastructure
-/dev/ci/*.sh      @ejgallego @SkySkimmer
-/.travis.yml      @ejgallego @SkySkimmer
-/.gitlab-ci.yml   @SkySkimmer @ejgallego
-/.appveyor.yml    @maximedenes @SkySkimmer
+########## CI infrastructure ##########
 
-/default.nix     @Zimmi48 @vbgl
+/dev/ci/*.sh      @ejgallego
+# Secondary maintainer @SkySkimmer
 
-# Documentation
-/README.md        @Zimmi48 @maximedenes
-/INSTALL*         @Zimmi48 @maximedenes
-/CONTRIBUTING.md  @Zimmi48 @maximedenes
-/dev/doc/         @Zimmi48 @maximedenes
-/doc/             @silene @maximedenes
-/man/             @silene @maximedenes
+/.travis.yml      @ejgallego
+# Secondary maintainer @SkySkimmer
 
-/checker/         @barras @maximedenes
+/.gitlab-ci.yml   @SkySkimmer
+# Secondary maintainer @ejgallego
 
-/clib/            @ppedrot @ejgallego
+/.appveyor.yml    @maximedenes
+# Secondary maintainer @SkySkimmer
 
+/default.nix     @Zimmi48
+# Secondary maintainer @vbgl
 
-/engine/          @ppedrot @aspiwack
+########## Documentation ##########
 
-/grammar/         @ppedrot @maximedenes
+/README.md        @Zimmi48
+# Secondary maintainer @maximedenes
 
-/ide/             @ppedrot @gares
+/INSTALL*         @Zimmi48
+# Secondary maintainer @maximedenes
 
-/interp/          @herbelin @ejgallego
+/CONTRIBUTING.md  @Zimmi48
+# Secondary maintainer @maximedenes
 
-/intf/            @letouzey @ppedrot
-/kernel/          @maximedenes @barras
-/kernel/byterun/  @maximedenes @silene
-/lib/             @ejgallego @ppedrot
-/library/         @silene @gares
+/dev/doc/         @Zimmi48
+# Secondary maintainer @maximedenes
 
-/parsing/         @herbelin @mattam82
+/doc/             @silene
+# Secondary maintainer @maximedenes
 
-/plugins/btauto/  @ppedrot @herbelin
+/man/             @silene
+# Secondary maintainer @maximedenes
+
+########## Coqchk ##########
+
+/checker/         @barras
+# Secondary maintainer @maximedenes
+
+########## Coq lib ##########
+
+/clib/            @ppedrot
+# Secondary maintainer @ejgallego
+
+/lib/             @ejgallego
+# Secondary maintainer @ppedrot
+
+########## Proof engine ##########
+
+/engine/          @ppedrot
+# Secondary maintainer @aspiwack
+
+########## Grammar macros ##########
+
+/grammar/         @ppedrot
+# Secondary maintainer @maximedenes
+
+########## CoqIDE ##########
+
+/ide/             @ppedrot
+# Secondary maintainer @gares
+
+########## Interpretation ##########
+
+/interp/          @herbelin
+# Secondary maintainer @ejgallego
+
+########## Interfaces ##########
+
+/intf/            @letouzey
+# Secondary maintainer @ppedrot
+
+########## Kernel ##########
+
+/kernel/          @maximedenes
+# Secondary maintainer @barras
+
+/kernel/byterun/  @maximedenes
+# Secondary maintainer @silene
+
+########## Library ##########
+
+/library/         @silene
+# Secondary maintainer @gares
+
+########## Parser ##########
+
+/parsing/         @herbelin
+# Secondary maintainer @mattam82
+
+########## Plugins ##########
+
+/plugins/btauto/  @ppedrot
+# Secondary maintainer @herbelin
 
 # I don't know Pierre Corbineau's GitHub nickname
 /plugins/cc/            @herbelin
 
-/plugins/derive/        @aspiwack @ppedrot
-/plugins/extraction/    @letouzey @maximedenes
+/plugins/derive/        @aspiwack
+# Secondary maintainer @ppedrot
 
- # I don't know Pierre Corbineau's GitHub nickname
+/plugins/extraction/    @letouzey
+# Secondary maintainer @maximedenes
+
+# I don't know Pierre Corbineau's GitHub nickname
 /plugins/firstorder/    @herbelin
 
-/plugins/fourier/       @herbelin @gares
-/plugins/funind/        @forestjulien @Matafou
+/plugins/fourier/       @herbelin
+# Secondary maintainer @gares
+
+/plugins/funind/        @forestjulien
+# Secondary maintainer @Matafou
+
 /plugins/ltac/          @ppedrot
-/plugins/micromega/     @fajb @bgregoir
-/plugins/nsatz/         @thery @ppedrot
+# Secondary maintainer @herbelin
+
+/plugins/micromega/     @fajb
+# Secondary maintainer @bgregoir
+
+/plugins/nsatz/         @thery
+# Secondary maintainer @ppedrot
+
 /plugins/omega/         @letouzey
+
 /plugins/romega/        @letouzey
-/plugins/setoid_ring/   @amahboubi @bgregoir
-/plugins/ssrmatching/   @gares @maximedenes
-/plugins/ssr/           @gares @maximedenes
-/plugins/syntax/        @ppedrot @maximedenes
 
+/plugins/setoid_ring/   @amahboubi
+# Secondary maintainer @bgregoir
+
+/plugins/ssrmatching/   @gares
+# Secondary maintainer @maximedenes
+
+/plugins/ssr/           @gares
+# Secondary maintainer @maximedenes
+
+/plugins/syntax/        @ppedrot
+# Secondary maintainer @maximedenes
 
 /plugins/quote/ @herbelin
 
 # Should be Pierre Corbineau too
 /plugins/rtauto/ @herbelin
 
-/pretyping/       @mattam82 @gares
-/printing/        @herbelin @mattam82
-
-/proofs/          @ppedrot @Zimmi48
-
-/stm/             @gares @ejgallego
-
-/tactics/         @ppedrot @mattam82
-
-/theories/Arith/          @letouzey @herbelin
-/theories/Bool/           @letouzey @herbelin
-/theories/Classes/        @mattam82 @herbelin
-/theories/FSets/          @letouzey @herbelin
-/theories/Init/           @letouzey @ppedrot
-/theories/Lists/          @letouzey @ppedrot
-/theories/Logic/          @herbelin @ppedrot
-/theories/MSets/          @letouzey @herbelin
-/theories/NArith/         @letouzey @herbelin
-/theories/Numbers/        @letouzey @herbelin
-/theories/PArith/         @letouzey @herbelin
-/theories/Program/        @mattam82 @herbelin
-/theories/QArith/         @letouzey @herbelin
-/theories/Reals/          @silene @ppedrot
-/theories/Relations/      @mattam82 @ppedrot
-/theories/Setoids/        @mattam82 @ppedrot
-/theories/Sets/           @letouzey @herbelin
-/theories/Sorting/        @letouzey @herbelin
-/theories/Strings/        @letouzey @herbelin
-/theories/Structures/     @letouzey @herbelin
-/theories/Unicode/        @letouzey @herbelin
-/theories/Wellfounded/    @letouzey @mattam82
-/theories/ZArith/         @letouzey @herbelin
-
-/theories/Compat/         @JasonGross @Zimmi48
+########## Pretyper ##########
+
+/pretyping/       @mattam82
+# Secondary maintainer @gares
+
+########## Pretty printer ##########
+
+/printing/        @herbelin
+# Secondary maintainer @mattam82
+
+########## Proof infrastructure ##########
+
+/proofs/          @ppedrot
+# Secondary maintainer @Zimmi48
+
+########## STM ##########
+
+/stm/             @gares
+# Secondary maintainer @ejgallego
+
+########## Tactics ##########
+
+/tactics/         @ppedrot
+# Secondary maintainer @mattam82
+
+########## Standard library ##########
+
+/theories/Arith/          @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Bool/           @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Classes/        @mattam82
+# Secondary maintainer @herbelin
+
+/theories/FSets/          @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Init/           @letouzey
+# Secondary maintainer @ppedrot
+
+/theories/Lists/          @letouzey
+# Secondary maintainer @ppedrot
+
+/theories/Logic/          @herbelin
+# Secondary maintainer @ppedrot
+
+/theories/MSets/          @letouzey
+# Secondary maintainer @herbelin
+
+/theories/NArith/         @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Numbers/        @letouzey
+# Secondary maintainer @herbelin
+
+/theories/PArith/         @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Program/        @mattam82
+# Secondary maintainer @herbelin
+
+/theories/QArith/         @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Reals/          @silene
+# Secondary maintainer @ppedrot
+
+/theories/Relations/      @mattam82
+# Secondary maintainer @ppedrot
+
+/theories/Setoids/        @mattam82
+# Secondary maintainer @ppedrot
+
+/theories/Sets/           @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Sorting/        @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Strings/        @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Structures/     @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Unicode/        @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Wellfounded/    @letouzey
+# Secondary maintainer @mattam82
+
+/theories/ZArith/         @letouzey
+# Secondary maintainer @herbelin
+
+/theories/Compat/         @JasonGross
+# Secondary maintainer @Zimmi48
 
 /theories/Vectors/        @herbelin
 
-/tools/coqdoc/          @silene @mattam82
-/tools/coq_makefile*    @gares @silene
-/tools/CoqMakefile*     @gares @silene
-/tools/coqdep*          @ppedrot @maximedenes
-/tools/coq_tex*         @silene @gares
-/tools/coqwc*           @silene @gares
+########## Tools ##########
+
+/tools/coqdoc/          @silene
+# Secondary maintainer @mattam82
+
+/tools/coq_makefile*    @gares
+# Secondary maintainer @silene
+
+/tools/CoqMakefile*     @gares
+# Secondary maintainer @silene
+
+/tools/coqdep*          @ppedrot
+# Secondary maintainer @maximedenes
+
+/tools/coq_tex*         @silene
+# Secondary maintainer @gares
+
+/tools/coqwc*           @silene
+# Secondary maintainer @gares
+
+########## Toplevel ##########
+
+/toplevel/        @ejgallego
+# Secondary maintainer @gares
+
+########## Vernacular ##########
+
+/vernac/          @mattam82
+# Secondary maintainer @maximedenes
+
+########## Build system ##########
+
+/Makefile*        @letouzey
+# Secondary maintainer @maximdenes
 
-/toplevel/        @ejgallego @gares
-/vernac/          @mattam82 @maximedenes
+/configure*       @letouzey
+# Secondary maintainer @ejgallego
 
-/Makefile*        @letouzey @ejgallego
-/configure*       @letouzey @ejgallego
-/META.coq         @letouzey @ejgallego
+/META.coq         @letouzey
+# Secondary maintainer @ejgallego