Add GZ_CONSOLE_COLOR env variable to control terminal color output

If the env variable is yes , the ANSI color codes are on for logging. When it is no, it disables ANSI colors
Fixes #611

Signed-off-by: BhuvanB <bhuvanb1408@gmail.com>

Author: BhuvanB404

README.md

@@ -61,6 +61,11 @@ See the [installation tutorial](https://gazebosim.org/api/common/7/install.html)
 
 Please refer to the [examples directory](https://github.com/gazebosim/gz-common/tree/gz-common7/examples).
 
+Console color output can be controlled with `GZ_CONSOLE_COLOR`:
+
+* `yes`: always emit ANSI color codes.
+* `no`: never emit ANSI color codes.
+
 # Folder Structure
 
 Refer to the following table for information about important directories and files in this repository.

src/Console.cc

@@ -85,6 +85,26 @@ Console &Console::Root()
 bool Console::Init(const std::string &_directory, const std::string &_filename)
 {
   std::string logPath;
+  std::string consoleColor;
+
+  if (env("GZ_CONSOLE_COLOR", consoleColor))
+  {
+    const auto value = lowercase(trimmed(consoleColor));
+
+    if (value == "yes")
+    {
+      Console::Root().SetConsoleColorMode(spdlog::color_mode::always);
+    }
+    else if (value == "no")
+    {
+      Console::Root().SetConsoleColorMode(spdlog::color_mode::never);
+    }
+    else
+    {
+      Console::Root().RawLogger().log(spdlog::level::warn,
+        "Valid values are: yes, no.");
+    }
+  }
 
   if (_directory.empty() ||
 #ifndef _WIN32