Enable color output in Windows cmd.exe

Git requires the TERM environment variable to be set for all color*
settings. Simulate the TERM variable if it is not set (default on Windows).

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

compat/mingw.c

@@ -640,6 +640,10 @@ char *mingw_getenv(const char *name)
 		if (!result)
 			result = getenv("TEMP");
 	}
+	else if (!result && !strcmp(name, "TERM")) {
+		/* simulate TERM to enable auto-color (see color.c) */
+		result = "winansi";
+	}
 	return result;
 }