feat: add git.workspace_path function

And refactor the git module.

src/git.zig

@@ -3,30 +3,101 @@ const tp = @import("thespian");
 const shell = @import("shell");
 const bin_path = @import("bin_path");
 
+pub const Error = error{ OutOfMemory, GitNotFound, GitCallFailed };
+
+const log_execute = false;
+
+pub fn workspace_path() Error!void {
+    const fn_name = @src().fn_name;
+    try git(.{ "rev-parse", "--show-toplevel" }, struct {
+        fn result(parent: tp.pid_ref, output: []const u8) void {
+            var it = std.mem.splitScalar(u8, output, '\n');
+            while (it.next()) |branch| if (branch.len > 0)
+                parent.send(.{ module_name, fn_name, branch }) catch {};
+        }
+    }.result, exit_null_on_error(fn_name));
+}
+
+pub fn current_branch() Error!void {
+    const fn_name = @src().fn_name;
+    try git(.{ "rev-parse", "--abbrev-ref", "HEAD" }, struct {
+        fn result(parent: tp.pid_ref, output: []const u8) void {
+            var it = std.mem.splitScalar(u8, output, '\n');
+            while (it.next()) |branch| if (branch.len > 0)
+                parent.send(.{ module_name, fn_name, branch }) catch {};
+        }
+    }.result, exit_null_on_error(fn_name));
+}
+
+fn git(
+    cmd: anytype,
+    out: OutputHandler,
+    exit: ExitHandler,
+) Error!void {
+    return git_err(cmd, out, noop, exit);
+}
+
+fn git_err(
+    cmd: anytype,
+    out: OutputHandler,
+    err: OutputHandler,
+    exit: ExitHandler,
+) Error!void {
+    const cbor = @import("cbor");
+    const git_binary = get_git() orelse return error.GitNotFound;
+    var buf: std.ArrayListUnmanaged(u8) = .empty;
+    const writer = buf.writer(allocator);
+    switch (@typeInfo(@TypeOf(cmd))) {
+        .@"struct" => |info| if (info.is_tuple) {
+            try cbor.writeArrayHeader(writer, info.fields.len + 1);
+            try cbor.writeValue(writer, git_binary);
+            inline for (info.fields) |f|
+                try cbor.writeValue(writer, @field(cmd, f.name));
+            return shell.execute(allocator, .{ .buf = buf.items }, .{
+                .out = to_shell_output_handler(out),
+                .err = to_shell_output_handler(err),
+                .exit = exit,
+                .log_execute = log_execute,
+            }) catch error.GitCallFailed;
+        },
+        else => {},
+    }
+    @compileError("git command should be a tuple: " ++ @typeName(@TypeOf(cmd)));
+}
+
+fn exit_null_on_error(comptime tag: []const u8) shell.ExitHandler {
+    return struct {
+        fn exit(_: usize, parent: tp.pid_ref, _: []const u8, _: []const u8, exit_code: i64) void {
+            if (exit_code > 0)
+                parent.send(.{ module_name, tag, null }) catch {};
+        }
+    }.exit;
+}
+
+const OutputHandler = fn (parent: tp.pid_ref, output: []const u8) void;
+const ExitHandler = shell.ExitHandler;
+
+fn to_shell_output_handler(handler: anytype) shell.OutputHandler {
+    return struct {
+        fn out(_: usize, parent: tp.pid_ref, _: []const u8, output: []const u8) void {
+            handler(parent, output);
+        }
+    }.out;
+}
+
+fn noop(_: tp.pid_ref, _: []const u8) void {}
+
 var git_path: ?struct {
     path: ?[:0]const u8 = null,
 } = null;
 
+const allocator = std.heap.c_allocator;
+
 fn get_git() ?[]const u8 {
     if (git_path) |p| return p.path;
-    const path = bin_path.find_binary_in_path(std.heap.c_allocator, "git") catch null;
+    const path = bin_path.find_binary_in_path(allocator, module_name) catch null;
     git_path = .{ .path = path };
     return path;
 }
 
-pub fn get_current_branch(allocator: std.mem.Allocator) !void {
-    const git_binary = get_git() orelse return error.GitBinaryNotFound;
-    const git_current_branch_cmd = tp.message.fmt(.{ git_binary, "rev-parse", "--abbrev-ref", "HEAD" });
-    const handlers = struct {
-        fn out(_: usize, parent: tp.pid_ref, _: []const u8, output: []const u8) void {
-            var it = std.mem.splitScalar(u8, output, '\n');
-            while (it.next()) |branch| if (branch.len > 0)
-                parent.send(.{ "git", "current_branch", branch }) catch {};
-        }
-    };
-    try shell.execute(allocator, git_current_branch_cmd, .{
-        .out = handlers.out,
-        .err = shell.log_err_handler,
-        .exit = shell.log_exit_err_handler,
-    });
-}
+const module_name = @typeName(@This());