Add test for systemwide config file support

There is now a new stage in the CICD workflow present, which will build
`bat` with the `BAT_SYSTEM_CONFIG_PREFIX` set to load the config file
from `/tests/examples/system_config/bat/config`, plus a basic set of
tests, to ensure the feature is working as expected. By default the
tests are set to ignored, as they need special setup before they can be
run.

tests/utils/command.rs

@@ -0,0 +1,36 @@
+use assert_cmd::cargo::CommandCargoExt;
+use std::process::Command;
+
+pub fn bat_raw_command_with_config() -> Command {
+    let mut cmd = Command::cargo_bin("bat").unwrap();
+    cmd.current_dir("tests/examples");
+    cmd.env_remove("BAT_CACHE_PATH");
+    cmd.env_remove("BAT_CONFIG_DIR");
+    cmd.env_remove("BAT_CONFIG_PATH");
+    cmd.env_remove("BAT_OPTS");
+    cmd.env_remove("BAT_PAGER");
+    cmd.env_remove("BAT_STYLE");
+    cmd.env_remove("BAT_TABS");
+    cmd.env_remove("BAT_THEME");
+    cmd.env_remove("COLORTERM");
+    cmd.env_remove("NO_COLOR");
+    cmd.env_remove("PAGER");
+    cmd
+}
+
+#[cfg(test)]
+pub fn bat_raw_command() -> Command {
+    let mut cmd = bat_raw_command_with_config();
+    cmd.arg("--no-config");
+    cmd
+}
+
+#[cfg(test)]
+pub fn bat_with_config() -> assert_cmd::Command {
+    assert_cmd::Command::from_std(bat_raw_command_with_config())
+}
+
+#[cfg(test)]
+pub fn bat() -> assert_cmd::Command {
+    assert_cmd::Command::from_std(bat_raw_command())
+}

tests/utils/mod.rs

@@ -1 +1,2 @@
+pub mod command;
 pub mod mocked_pagers;