Pipfile自动定位是否有目录深度限制？pipenv三级子目录无法识别项目

我的项目采用三级目录结构，发现从三级及更深层级的目录执行pipenv命令时，无法识别当前处于pipenv项目中。

演示过程 #

$ env -i sh -l
$ mkdir /tmp/myproject
$ cd /tmp/myproject
$ pipenv --where
No Pipfile present at project home. Consider running `pipenv install` first to automatically generate a Pipfile for you.

$ touch Pipfile
$ pipenv --where
/tmp/myproject

$ mkdir -p a/b/c/d

$ cd a
$ pipenv --where  
/tmp/myproject

$ cd b
$ pipenv --where
/tmp/myproject

$ cd c
$ pipenv --where
No Pipfile present at project home. Consider running `pipenv install` first to automatically generate a Pipfile for you.

$ cd d
$ pipenv --where
No Pipfile present at project home. Consider running `pipenv install` first to automatically generate a Pipfile for you.

可见一级、二级子目录中pipenv能识别父目录的Pipfile，但更深目录则不行。这是bug还是特性？我查阅了大量文档，甚至调试pipenv试图定位原因，但未找到相关内容。

调试详情 #

$ pipenv --support
Pipenv version: `'2022.7.4'`
Pipenv location: `'/usr/lib/python3.10/site-packages/pipenv'`
Python location: `'/usr/bin/python'`
Python installations found:

  - `3.10.5`: `/usr/bin/python`
  - `3.10.5`: `/usr/bin/python3`

PEP 508 Information:

{'implementation_name': 'cpython',
'implementation_version': '3.10.5',
'os_name': 'posix',
'platform_machine': 'x86_64',
'platform_python_implementation': 'CPython',
'platform_release': '5.10.120-16471-g167ad2e5dcba',
'platform_system': 'Linux',
'platform_version': '#1 SMP PREEMPT Fri Jul 29 18:58:29 PDT 2022',
'python_full_version': '3.10.5',
'python_version': '3.10',
'sys_platform': 'linux'}

System environment variables:

  - `LESSCHARSET`
  - `EDITOR`
  - `PWD`
  - `LANG`
  - `VISUAL`
  - `SHLVL`
  - `PATH`
  - `_`
  - `OLDPWD`
  - `LC_CTYPE`
  - `PIP_SHIMS_BASE_MODULE`
  - `PIP_DISABLE_PIP_VERSION_CHECK`
  - `PIP_PYTHON_PATH`
  - `PYTHONDONTWRITEBYTECODE`
  - `PYTHONFINDER_IGNORE_UNSUPPORTED`

Pipenv–specific environment variables:

(none)

Debug–specific environment variables:

  - `PATH`: `/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl`
  - `EDITOR`: `nvim`
  - `LANG`: `en_US.UTF-8`
  - `PWD`: `/tmp/myproject/a/b/c/d`

内容的提问来源于stack exchange，提问作者bukzor