不需要的unicode字符在终端 * 上打印时会转换为<U+0085>或<U+0086> * 等序列。
faulty=$(git branch | grep -a feature/my-branch)应该保存该分支名称的“正确”值，所以这应该可以工作：

# The '-a' option to grep is there to skip grep's auto detection of binary content
# it could kick in if there was a '\x00' byte in the input
#
# Your specific issue (with <U+0085> characters) shouldn't trigger it, I'm just
# mentioning that option for a more general scope
faulty=$(git branch | grep -a feature/my-branch)

# to avoid shenanigans with leading spaces and a possible '*' in the output:
faulty=$(git branch --format="%(refname:short)" | grep -a feature/my-branch)

git branch -m "$faulty" feature/my-branch

否则：printf知道如何解释\uXXXX序列。
您可以尝试运行：

faulty=$(printf "\u0085\u0085\u0085\u0086feature/my-branch")
# you can check if 'echo "$faulty"' gives you the same output as 'git branch'

git branch -m "$faulty" feature/my-branch

bash本身应该知道，当使用$'...'语法来解释转义序列时：

git branch -m $'\u0085\u0085\u0085\u0086feature/my-branch' feature/my-branch