contrib/completion/git-completion.bash: declare -g is not portable

From: Torsten Bögershausen <tboegi@web.de>
Date: Feb 3, 2018, 17:20 UTC
Message-ID: <1e618c0c-81ba-fa7e-8039-748bdfa5a6d9@web.de>

Hej Duy, After running t9902-completion.sh on Mac OS I got a failure in this style:

.../projects/git/git.pu/t/../contrib/completion/git-completion.bash: line 300: declare: -g: invalid option declare: usage: declare [-afFirtx] [-p] [name[=value] ...] --- expected 2018-02-03 17:10:18.000000000 +0000 +++ out 2018-02-03 17:10:18.000000000 +0000

@@ -1,15 +1,2 @@
---quiet
---detach
---track
---orphan=
---ours
---theirs
---merge
---conflict=
---patch
---ignore-skip-worktree-bits
---ignore-other-worktrees
---recurse-submodules
---progress
 --no-track
 --no-recurse-submodules
not ok 92 - double dash "git checkout"

What is "declare -g" good for ?

<https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html#index-declare>