私が言えることから、それはGitの問題ではなく、GNU gettextの問題です。
バグはGNU gettext v0.20で修正されたようです。しかし、この投稿の時点で、Homebrewは残念ながらv0.19.8.1のみを提供しています。
次のように問題を再現しました。
$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.14.4
BuildVersion: 18E226
$ locale
LANG=
LC_COLLATE="C"
LC_CTYPE="UTF-8"
LC_MESSAGES="C"
LC_MONETARY="C"
LC_NUMERIC="C"
LC_TIME="C"
LC_ALL=
$ defaults read -g AppleLanguages
(
"en-JP",
"ja-JP",
"sv-JP"
)
$ brew info gettext
gettext: stable 0.19.8.1 (bottled) [keg-only]
GNU internationalization (i18n) and localization (l10n) library
https://www.gnu.org/software/gettext/
/usr/local/Cellar/gettext/0.19.8.1 (1,934 files, 17.0MB)
Poured from bottle on 2016-06-24 at 02:05:52
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/gettext.rb
...
$ /usr/local/Cellar/gettext/0.19.8.1/bin/msgcat --version
msgcat (GNU gettext-tools) 0.19.8.1
Copyright (c) 2001-2016 Free Software Foundation, Inc.
Licens GPLv3+: GNU GPL version 3 eller senare <http://gnu.org/licenses/gpl.html>
Detta program "ar fri programvara. Du kan modifiera och distribuera den.
Det finns inte NAGON SOM HELST GARANTI, till den grad som lagen tillater.
Skrivet av Bruno Haible.
$ sudo filebyproc.d
CPU ID FUNCTION:NAME
...
2 957 open_nocancel:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/bin
2 957 open_nocancel:entry msgcat /etc/localtime
2 957 open_nocancel:entry msgcat /var/db/timezone/zoneinfo/posixrules
2 957 open_nocancel:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/locale.alias
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/en_JP/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/en/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja_JP.eucJP/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja_JP.eucjp/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja_JP/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja.eucJP/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja.eucjp/LC_MESSAGES/gettext-tools.mo
2 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/ja/LC_MESSAGES/gettext-tools.mo
3 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/sv_JP/LC_MESSAGES/gettext-tools.mo
3 171 open:entry msgcat /usr/local/Cellar/gettext/0.19.8.1/share/locale/sv/LC_MESSAGES/gettext-tools.mo