CLI: Add 'cd' subcommand (#12584)

* CLI: Add 'cd' subcommand

Go to your qmk_firmware dir with ease.

* Fix for Windows and do not run if already under QMK Home

* Make flake8 happy

* Fix prompt for Windows

* Make flake8 happy once again

* I'll get it right eventually

* Apply suggestions from code review

Co-authored-by: Ryan <fauxpark@gmail.com>

* Add subcommand to __init__.py and fixup after rebase

* Update Windows code to use milc's run

* Unify the subshell starting with os.execl

* Exit with error msg when output is redirected to non-TTY.

* Revert Windows-specific code

Co-authored-by: Ryan <fauxpark@gmail.com>

3 files changed, 61 insertions, 0 deletions

diff --git a/docs/cli_commands.md b/docs/cli_commands.md
index e498f3b22e..8f5117633f 100644
--- a/docs/cli_commands.md
+++ b/docs/cli_commands.md
@@ -118,6 +118,20 @@ This command lets you configure the behavior of QMK. For the full `qmk config` d
 qmk config [-ro] [config_token1] [config_token2] [...] [config_tokenN]
 ```
 
+## `qmk cd`
+
+This command opens a new shell in your `qmk_firmware` directory.
+
+Note that if you are already somewhere within `QMK_HOME` (for example, the `keyboards/` folder), nothing will happen.
+
+To exit out into the parent shell, simply type `exit`.
+
+**Usage**:
+
+```
+qmk cd
+```
+
 ## `qmk console`
 
 This command lets you connect to keyboard consoles to get debugging messages. It only works if your keyboard firmware has been compiled with `CONSOLE_ENABLE=yes`.
diff --git a/lib/python/qmk/cli/__init__.py b/lib/python/qmk/cli/__init__.py
index 539d03e2fc..ea961315bd 100644
--- a/lib/python/qmk/cli/__init__.py
+++ b/lib/python/qmk/cli/__init__.py
@@ -31,6 +31,7 @@ safe_commands = [
 subcommands = [
     'qmk.cli.bux',
     'qmk.cli.c2json',
+    'qmk.cli.cd',
     'qmk.cli.cformat',
     'qmk.cli.chibios.confmigrate',
     'qmk.cli.clean',
diff --git a/lib/python/qmk/cli/cd.py b/lib/python/qmk/cli/cd.py
new file mode 100755
index 0000000000..c62c3f56c6
--- /dev/null
+++ b/lib/python/qmk/cli/cd.py
@@ -0,0 +1,46 @@
+"""Open a shell in the QMK Home directory
+"""
+import sys
+import os
+
+from milc import cli
+
+from qmk.path import under_qmk_firmware
+
+
+@cli.subcommand('Go to QMK Home')
+def cd(cli):
+    """Go to QMK Home
+    """
+    if not sys.stdout.isatty():
+        cli.log.error("This command is for interactive usage only. For non-interactive usage, 'cd $(qmk env QMK_HOME)' is more robust.")
+        sys.exit(1)
+
+    if not under_qmk_firmware():
+        # Only do anything if the user is not under qmk_firmware already
+        # in order to reduce the possibility of starting multiple shells
+        cli.log.info("Spawning a subshell in your QMK_HOME directory.")
+        cli.log.info("Type 'exit' to get back to the parent shell.")
+        if not cli.platform.lower().startswith('windows'):
+            # For Linux/Mac/etc
+            # Check the user's login shell from 'passwd'
+            # alternatively fall back to $SHELL env var
+            # and finally to '/bin/bash'.
+            import getpass
+            import pwd
+            shell = pwd.getpwnam(getpass.getuser()).pw_shell
+            if not shell:
+                shell = os.environ.get('SHELL', '/bin/bash')
+            # Start the new subshell
+            os.execl(shell, shell)
+        else:
+            # For Windows
+            # Check the $SHELL env var
+            # and fall back to '/usr/bin/bash'.
+            qmk_env = os.environ.copy()
+            # Set the prompt for the new shell
+            qmk_env['MSYS2_PS1'] = qmk_env['PS1']
+            # Start the new subshell
+            cli.run([os.environ.get('SHELL', '/usr/bin/bash')], env=qmk_env)
+    else:
+        cli.log.info("Already within qmk_firmware directory.")