scripts: Auto-detect whether we can enable colors

Also do the setup necessary on Windows to enable ANSI colours on the
console (if available). That code is copied from Meson and is Apache2
licensed.

checkout-branch-worktree

@@ -73,7 +73,7 @@ if __name__ == "__main__":
                         help="The meson build directory")
     options = parser.parse_args()
 
-    if options.no_color:
+    if options.no_color or not Colors.can_enable():
         Colors.disable()
 
     if not os.path.exists(options.builddir):

common.py

@@ -1,9 +1,10 @@
-import argparse
 import os
 import sys
-import shutil
-import subprocess
 import shlex
+import shutil
+import argparse
+import platform
+import subprocess
 
 
 ROOTDIR = os.path.abspath(os.path.dirname(__file__))
@@ -19,6 +20,27 @@ class Colors:
 
     force_disable = False
 
+    def _windows_ansi():
+        from ctypes import windll, byref
+        from ctypes.wintypes import DWORD
+
+        kernel = windll.kernel32
+        stdout = kernel.GetStdHandle(-11)
+        mode = DWORD()
+        if not kernel.GetConsoleMode(stdout, byref(mode)):
+            return False
+        # Try setting ENABLE_VIRTUAL_TERMINAL_PROCESSING (0x4)
+        # If that fails (returns 0), we disable colors
+        return kernel.SetConsoleMode(stdout, mode.value | 0x4) or os.environ.get('ANSICON')
+
+    @classmethod
+    def can_enable(cls):
+        if not os.isatty(sys.stdout.fileno()):
+            return False
+        if platform.system().lower() == 'windows':
+            return cls._windows_ansi()
+        return os.environ.get('TERM') != 'dumb'
+
     @classmethod
     def disable(cls):
         cls.HEADER = ''
@@ -44,7 +66,8 @@ class Colors:
 
 def git(*args, repository_path='.'):
     return subprocess.check_output(["git"] + list(args), cwd=repository_path,
-                                   ).decode()
+                                   stdin=subprocess.DEVNULL,
+                                   stderr=subprocess.STDOUT).decode()
 
 def accept_command(commands):
     """Search @commands and returns the first found absolute path."""

git-update

@@ -136,7 +136,7 @@ if __name__ == "__main__":
                         help="Use a android repo manifest to sync repositories"
                         " Note that it will let all repositories in detached state")
     options = parser.parse_args()
-    if options.no_color:
+    if options.no_color or not Colors.can_enable():
         Colors.disable()
 
     if options.no_interaction: