Add --ignore-config command line option

ncdu.pod

@@ -73,6 +73,10 @@ information.
 This enables viewing and sorting by the latest child mtime, or modified time,
 using 'm' and 'M', respectively.
 
+=item --ignore-config
+
+Do not attempt to load any configuration files.
+
 =back
 
 =head2 Scan Options
@@ -272,7 +276,8 @@ Ncdu can be configured by placing command-line options in C</etc/ncdu.conf> or
 C<$HOME/.config/ncdu/config>. If both files exist, the system configuration
 will be loaded before the user configuration, allowing users to override
 options set in the system configuration. Options given on the command line will
-override options set in the configuration files.
+override options set in the configuration files. The files will not be read at
+all when C<--ignore-config> is given on the command line.
 
 The configuration file format is simply one command line option per line. Lines
 starting with C<#> are ignored. Example configuration file:

src/main.zig

@@ -306,6 +306,7 @@ fn help() noreturn {
     \\  --exclude-kernfs           Exclude Linux pseudo filesystems (procfs,sysfs,cgroup,...)
     \\  --confirm-quit             Confirm quitting ncdu
     \\  --color SCHEME             Set color scheme (off/dark/dark-bg)
+    \\  --ignore-config            Don't load config files
     \\
     \\Refer to `man ncdu` for the full list of options.
     \\
@@ -394,6 +395,15 @@ pub fn main() void {
     }
     if (std.os.getenvZ("NO_COLOR") == null) config.ui_color = .darkbg;
 
+    const loadConf = blk: {
+        var args = std.process.ArgIteratorPosix.init();
+        while (args.next()) |a|
+            if (std.mem.eql(u8, a, "--ignore-config"))
+                break :blk false;
+        break :blk true;
+    };
+
+    if (loadConf) {
         tryReadArgsFile("/etc/ncdu.conf");
 
         if (std.os.getenvZ("XDG_CONFIG_HOME")) |p| {
@@ -405,6 +415,7 @@ pub fn main() void {
             defer allocator.free(path);
             tryReadArgsFile(path);
         }
+    }
 
     var scan_dir: ?[]const u8 = null;
     var import_file: ?[:0]const u8 = null;
@@ -427,6 +438,7 @@ pub fn main() void {
             else if (opt.is("-o")) export_file = allocator.dupeZ(u8, args.arg()) catch unreachable
             else if (opt.is("-f") and import_file != null) ui.die("The -f flag can only be given once.\n", .{})
             else if (opt.is("-f")) import_file = allocator.dupeZ(u8, args.arg()) catch unreachable
+            else if (opt.is("--ignore-config")) {}
             else if (argConfig(&args, opt)) {}
             else ui.die("Unrecognized option '{s}'.\n", .{opt.val});
         }