[build, devscripts] Add devscript to set a build variant

Closes #4471

4 files changed, 21 insertions, 9 deletions

diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index ded34b8ed..228aa7bf5 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -144,7 +144,7 @@ from .utils import (
     write_json_file,
     write_string,
 )
-from .version import RELEASE_GIT_HEAD, __version__
+from .version import RELEASE_GIT_HEAD, VARIANT, __version__
 
 if compat_os_name == 'nt':
     import ctypes
@@ -3676,6 +3676,8 @@ class YoutubeDL:
             write_debug = lambda msg: self._write_string(f'[debug] {msg}\n')
 
         source = detect_variant()
+        if VARIANT not in (None, 'pip'):
+            source += '*'
         write_debug(join_nonempty(
             'yt-dlp version', __version__,
             f'[{RELEASE_GIT_HEAD}]' if RELEASE_GIT_HEAD else '',
diff --git a/yt_dlp/options.py b/yt_dlp/options.py
index b70f5798e..2c7f686dd 100644
--- a/yt_dlp/options.py
+++ b/yt_dlp/options.py
@@ -20,12 +20,13 @@ from .postprocessor import (
     SponsorBlockPP,
 )
 from .postprocessor.modify_chapters import DEFAULT_SPONSORBLOCK_CHAPTER_TITLE
-from .update import detect_variant
+from .update import detect_variant, is_non_updateable
 from .utils import (
     OUTTMPL_TYPES,
     POSTPROCESS_WHEN,
     Config,
     expand_path,
+    format_field,
     get_executable_path,
     join_nonempty,
     remove_end,
@@ -333,11 +334,13 @@ def create_parser():
     general.add_option(
         '-U', '--update',
         action='store_true', dest='update_self',
-        help='Update this program to latest version')
+        help=format_field(
+            is_non_updateable(), None, 'Check if updates are available. %s',
+            default='Update this program to the latest version'))
     general.add_option(
         '--no-update',
         action='store_false', dest='update_self',
-        help='Do not update (default)')
+        help='Do not check for updates (default)')
     general.add_option(
         '-i', '--ignore-errors',
         action='store_true', dest='ignoreerrors',
diff --git a/yt_dlp/update.py b/yt_dlp/update.py
index 92c07acc1..a04518c9b 100644
--- a/yt_dlp/update.py
+++ b/yt_dlp/update.py
@@ -18,7 +18,7 @@ from .utils import (
     traverse_obj,
     version_tuple,
 )
-from .version import __version__
+from .version import UPDATE_HINT, VARIANT, __version__
 
 REPOSITORY = 'yt-dlp/yt-dlp'
 API_URL = f'https://api.github.com/repos/{REPOSITORY}/releases'
@@ -47,7 +47,7 @@ def _get_variant_and_executable_path():
 
 
 def detect_variant():
-    return _get_variant_and_executable_path()[0]
+    return VARIANT or _get_variant_and_executable_path()[0]
 
 
 _FILE_SUFFIXES = {
@@ -64,13 +64,16 @@ _NON_UPDATEABLE_REASONS = {
     **{variant: f'Auto-update is not supported for unpackaged {name} executable; Re-download the latest release'
        for variant, name in {'win32_dir': 'Windows', 'darwin_dir': 'MacOS', 'linux_dir': 'Linux'}.items()},
     'source': 'You cannot update when running from source code; Use git to pull the latest changes',
-    'unknown': 'It looks like you installed yt-dlp with a package manager, pip or setup.py; Use that to update',
-    'other': 'It looks like you are using an unofficial build of yt-dlp; Build the executable again',
+    'unknown': 'You installed yt-dlp with a package manager or setup.py; Use that to update',
+    'other': 'You are using an unofficial build of yt-dlp; Build the executable again',
 }
 
 
 def is_non_updateable():
-    return _NON_UPDATEABLE_REASONS.get(detect_variant(), _NON_UPDATEABLE_REASONS['other'])
+    if UPDATE_HINT:
+        return UPDATE_HINT
+    return _NON_UPDATEABLE_REASONS.get(
+        detect_variant(), _NON_UPDATEABLE_REASONS['unknown' if VARIANT else 'other'])
 
 
 def _sha256_file(path):
diff --git a/yt_dlp/version.py b/yt_dlp/version.py
index a1a5880e9..75ede4973 100644
--- a/yt_dlp/version.py
+++ b/yt_dlp/version.py
@@ -3,3 +3,7 @@
 __version__ = '2022.07.18'
 
 RELEASE_GIT_HEAD = '135f05ef6'
+
+VARIANT = None
+
+UPDATE_HINT = None