[RFC PATCH 08/13] tui: The _suspend_to_shell function assumes a POSIX environment, relying on $SHELL and shell-specific arguments (e.g., --rcfile) that are invalid on Windows.

[Adrian Neftali Sanchez <lutgaru@gmail.com>]

Refactor the execution flow to branch on sys.platform. On Windows,
launch the native interpreter via COMSPEC (defaulting to cmd.exe).
Move the existing POSIX-specific logic for bash/zsh into an explicit
else-block to ensure clean separation of platform execution paths.

This enables Windows support while preventing POSIX shell configuration
side effects on non-POSIX systems.

Signed-off-by: Adrian Neftali Sanchez <lutgaru@gmail.com>
---
 src/b4/tui/_common.py | 58 ++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 26 deletions(-)

diff --git a/src/b4/tui/_common.py b/src/b4/tui/_common.py
index cdd3818..6c8042c 100644
--- a/src/b4/tui/_common.py
+++ b/src/b4/tui/_common.py
@@ -10,6 +10,7 @@ __author__ = 'Konstantin Ryabitsev <konstantin@linuxfoundation.org>'
 import email.utils
 import os
 import subprocess
+import sys
 import tempfile
 import unicodedata
 from collections import defaultdict
@@ -198,36 +199,41 @@ def _suspend_to_shell(hint: str = 'b4', cwd: Optional[str] = None) -> None:
     logger.info('When done, Ctrl-d to return to review UI.')
     logger.info('---')
 
-    shell = os.environ.get('SHELL', '/bin/sh')
-    shellname = os.path.basename(shell)
     env = os.environ.copy()
     env['B4_REVIEW'] = hint
 
-    if shellname == 'bash':
-        bashrc = os.path.expanduser('~/.bashrc')
-        source = f'[ -f {bashrc} ] && . {bashrc}\n'
-        source += f'PS1="({hint}) $PS1"\n'
-        with tempfile.NamedTemporaryFile(
-            mode='w', prefix='b4-shell-', suffix='.sh', delete=False
-        ) as rcf:
-            rcf.write(source)
-            rcfile = rcf.name
-        try:
-            subprocess.run([shell, '--rcfile', rcfile], env=env, cwd=cwd)
-        finally:
-            os.unlink(rcfile)
-    elif shellname == 'zsh':
-        real_zdotdir = os.environ.get('ZDOTDIR', os.path.expanduser('~'))
-        with tempfile.TemporaryDirectory(prefix='b4-shell-') as tmpdir:
-            zshrc = os.path.join(tmpdir, '.zshrc')
-            with open(zshrc, 'w') as f:
-                f.write(f'ZDOTDIR="{real_zdotdir}"\n')
-                f.write('[ -f "$ZDOTDIR/.zshrc" ] && . "$ZDOTDIR/.zshrc"\n')
-                f.write(f'PS1="({hint}) $PS1"\n')
-            env['ZDOTDIR'] = tmpdir
-            subprocess.run([shell], env=env, cwd=cwd)
-    else:
+    if sys.platform == 'win32':
+        shell = os.environ.get('COMSPEC', 'cmd.exe')
         subprocess.run([shell], env=env, cwd=cwd)
+    else:
+        shell = os.environ.get('SHELL', '/bin/sh')
+        shellname = os.path.basename(shell)
+
+        if shellname == 'bash':
+            bashrc = os.path.expanduser('~/.bashrc')
+            source = f'[ -f {bashrc} ] && . {bashrc}\n'
+            source += f'PS1="({hint}) $PS1"\n'
+            with tempfile.NamedTemporaryFile(
+                mode='w', prefix='b4-shell-', suffix='.sh', delete=False
+            ) as rcf:
+                rcf.write(source)
+                rcfile = rcf.name
+            try:
+                subprocess.run([shell, '--rcfile', rcfile], env=env, cwd=cwd)
+            finally:
+                os.unlink(rcfile)
+        elif shellname == 'zsh':
+            real_zdotdir = os.environ.get('ZDOTDIR', os.path.expanduser('~'))
+            with tempfile.TemporaryDirectory(prefix='b4-shell-') as tmpdir:
+                zshrc = os.path.join(tmpdir, '.zshrc')
+                with open(zshrc, 'w') as f:
+                    f.write(f'ZDOTDIR="{real_zdotdir}"\n')
+                    f.write('[ -f "$ZDOTDIR/.zshrc" ] && . "$ZDOTDIR/.zshrc"\n')
+                    f.write(f'PS1="({hint}) $PS1"\n')
+                env['ZDOTDIR'] = tmpdir
+                subprocess.run([shell], env=env, cwd=cwd)
+        else:
+            subprocess.run([shell], env=env, cwd=cwd)
 
 
 def _addrs_to_lines(header_str: str) -> str:
-- 
2.45.0.windows.1