populateFileSystemInputs

    pub fn populateFileSystemInputs(man: *Manifest, buf: *std.ArrayList(u8)) Allocator.Error!void {
        assert(@typeInfo(std.zig.Server.Message.PathPrefix).@"enum".field_names.len == man.cache.prefixes_len);
        buf.clearRetainingCapacity();
        const gpa = man.cache.gpa;
        const files = man.files.keys();
        if (files.len > 0) {
            for (files) |file| {
                try buf.ensureUnusedCapacity(gpa, file.prefixed_path.sub_path.len + 2);
                buf.appendAssumeCapacity(file.prefixed_path.prefix + 1);
                buf.appendSliceAssumeCapacity(file.prefixed_path.sub_path);
                buf.appendAssumeCapacity(0);
            }
            // The null byte is a separator, not a terminator.
            buf.items.len -= 1;
        }
    }