Automatic release update warnings. (#1336)

* Hide pretty help

* Automatic release update warnings.

* `httpie cli check-updates`

* adapt to the new loglevel construct

* Don't make the pie-colors the bold

* Apply review feedback.

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>

httpie/internal/daemons.py

@@ -0,0 +1,121 @@
+"""
+This module provides an interface to spawn a detached task to be
+runned with httpie.internal.daemon_runner on a separate process. It is
+based on DVC's daemon system.
+https://github.com/iterative/dvc/blob/main/dvc/daemon.py
+"""
+
+import inspect
+import os
+import platform
+import sys
+import httpie.__main__
+from contextlib import suppress
+from subprocess import Popen
+from typing import Dict, List
+from httpie.compat import is_frozen, is_windows
+
+
+ProcessContext = Dict[str, str]
+
+
+def _start_process(cmd: List[str], **kwargs) -> Popen:
+    prefix = [sys.executable]
+    # If it is frozen, sys.executable points to the binary (http).
+    # Otherwise it points to the python interpreter.
+    if not is_frozen:
+        main_entrypoint = httpie.__main__.__file__
+        prefix += [main_entrypoint]
+    return Popen(prefix + cmd, close_fds=True, shell=False, **kwargs)
+
+
+def _spawn_windows(cmd: List[str], process_context: ProcessContext) -> None:
+    from subprocess import (
+        CREATE_NEW_PROCESS_GROUP,
+        CREATE_NO_WINDOW,
+        STARTF_USESHOWWINDOW,
+        STARTUPINFO,
+    )
+
+    # https://stackoverflow.com/a/7006424
+    # https://bugs.python.org/issue41619
+    creationflags = CREATE_NEW_PROCESS_GROUP | CREATE_NO_WINDOW
+
+    startupinfo = STARTUPINFO()
+    startupinfo.dwFlags |= STARTF_USESHOWWINDOW
+
+    _start_process(
+        cmd,
+        env=process_context,
+        creationflags=creationflags,
+        startupinfo=startupinfo,
+    )
+
+
+def _spawn_posix(args: List[str], process_context: ProcessContext) -> None:
+    """
+    Perform a double fork procedure* to detach from the parent
+    process so that we don't block the user even if their original
+    command's execution is done but the release fetcher is not.
+
+    [1]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap11.html#tag_11_01_03
+    """
+
+    from httpie.core import main
+
+    try:
+        pid = os.fork()
+        if pid > 0:
+            return
+    except OSError:
+        os._exit(1)
+
+    os.setsid()
+
+    try:
+        pid = os.fork()
+        if pid > 0:
+            os._exit(0)
+    except OSError:
+        os._exit(1)
+
+    # Close all standard inputs/outputs
+    sys.stdin.close()
+    sys.stdout.close()
+    sys.stderr.close()
+
+    if platform.system() == 'Darwin':
+        # Double-fork is not reliable on MacOS, so we'll use a subprocess
+        # to ensure the task is isolated properly.
+        process = _start_process(args, env=process_context)
+        # Unlike windows, since we already completed the fork procedure
+        # we can simply join the process and wait for it.
+        process.communicate()
+    else:
+        os.environ.update(process_context)
+        with suppress(BaseException):
+            main(['http'] + args)
+
+    os._exit(0)
+
+
+def _spawn(args: List[str], process_context: ProcessContext) -> None:
+    """
+    Spawn a new process to run the given command.
+    """
+    if is_windows:
+        _spawn_windows(args, process_context)
+    else:
+        _spawn_posix(args, process_context)
+
+
+def spawn_daemon(task: str) -> None:
+    args = [task, '--daemon']
+    process_context = os.environ.copy()
+    if not is_frozen:
+        file_path = os.path.abspath(inspect.stack()[0][1])
+        process_context['PYTHONPATH'] = os.path.dirname(
+            os.path.dirname(os.path.dirname(file_path))
+        )
+
+    _spawn(args, process_context)