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.

3 files changed, 28 insertions, 5 deletions

diff --git a/checkout-branch-worktree b/checkout-branch-worktree
index 3b29e73771..7f2dbd5185 100755
--- a/checkout-branch-worktree
+++ b/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):
diff --git a/common.py b/common.py
index 7f16391511..a9eca335b1 100644
--- a/common.py
+++ b/common.py
@@ -1,9 +1,10 @@
-import argparse
 import os
 import sys
+import shlex
 import shutil
+import argparse
+import platform
 import subprocess
-import shlex
 
 
 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."""
diff --git a/git-update b/git-update
index ce1a1099ad..71c6d038a1 100755
--- a/git-update
+++ b/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: