docs: print usage details to standard output if a help flag is used in command (#7)

Author: zimeg

CHANGELOG.md

@@ -7,6 +7,10 @@ to [Semantic Versioning][semver].
 
 ## [Unreleased]
 
+### Added
+
+- Print usage details to standard output if a help flag is used in command.
+
 ### Maintenance
 
 - Confirm code formatting matches the standard expectations about language.

README.md

@@ -10,6 +10,12 @@ The following command uses `git` details:
 $ git coverage  # https://app.codecov.io/gh/zimeg/git-coverage
 ```
 
+### Flags
+
+Options are available for customization:
+
+- `--help`: boolean. Print these usage details. Default: `false`
+
 ## Installation
 
 Add a build to `$PATH` for automatic detection.

src/main.zig

@@ -1,10 +1,49 @@
 const std = @import("std");
 
+const Flags = struct {
+    help: bool,
+
+    pub fn init(allocator: std.mem.Allocator) !Flags {
+        var flags = Flags{
+            .help = false,
+        };
+        var args = try std.process.argsWithAllocator(allocator);
+        _ = args.next();
+        while (true) {
+            const opt = args.next();
+            if (opt) |arg| {
+                if (std.mem.eql(u8, arg, "-h") or std.mem.eql(u8, arg, "--help")) {
+                    flags.help = true;
+                    break;
+                } else {
+                    return error.FlagOptionMissing;
+                }
+            } else {
+                break;
+            }
+        }
+        return flags;
+    }
+};
+
 pub fn main() !void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     var aa = std.heap.ArenaAllocator.init(gpa.allocator());
     defer aa.deinit();
     const allocator = aa.allocator();
+    const writer = std.io.getStdOut().writer();
+    const flags = try Flags.init(allocator);
+    if (flags.help) {
+        try writer.print(
+            \\usage: git coverage [options]
+            \\
+            \\Open test coverage uploaded to codecov in a web browser.
+            \\
+            \\    --help    boolean  print these usage details (default: false)
+            \\
+        , .{});
+        return;
+    }
     const proc = try std.process.Child.run(.{
         .allocator = allocator,
         .argv = &.{ "git", "remote", "-v" },
@@ -19,7 +58,7 @@ pub fn main() !void {
         .allocator = allocator,
         .argv = &[_][]const u8{ "open", url },
     }) catch {
-        try std.io.getStdOut().writer().print("{s}\n", .{url});
+        try writer.print("{s}\n", .{url});
     };
 }