[PATCH] autotest: Respect NO_COLOR in test suites.

[Nick Bowler]

This implements support for NO_COLOR in test suites using AT_COLOR_TESTS
to enable colour by default.  NO_COLOR is an informal standard[1] way
for users to express their preference to not use colours by default.

If NO_COLOR is set in the environment to anything other than the empty
string, the default should be "no colour" (but the command-line --color
option is expected to work as usual).

[1] http://no-color.org

* lib/autotest/general.m4 (AT_INIT): Respect user NO_COLOR setting
to restrict enabling of ANSI colours by default.
---
 lib/autotest/general.m4 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/autotest/general.m4 b/lib/autotest/general.m4
index 6b4c3ae5..b5388da4 100644
--- a/lib/autotest/general.m4
+++ b/lib/autotest/general.m4
@@ -446,7 +446,9 @@ m4_define([_AT_FINISH],
 m4_divert_text([DEFAULTS],
 [
 # Whether to enable colored test results.
-at_color=m4_ifdef([AT_color], [AT_color], [no])
+m4_ifdef([AT_color],
+  [AS_CASE([$NO_COLOR], [''], [at_color=auto], [at_color=no])],
+  [at_color=no])
 # As many question marks as there are digits in the last test group number.
 # Used to normalize the test group numbers so that 'ls' lists them in
 # numerical order.
-- 
2.45.2