Taskwarrior is an open-source cross platform command-line task management tool. It allows you to capture, annotate, manipulate and present your tasks, then sync them among devices.
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Pros

Pro Command line interface
The command line interface puts powerful filtering expressions, context, annotations, tags, due dates, reoccurrence, and user-defined-attributes totally in your hands. It’s fast and low friction.
Pro Extensible
Taskwarrior has many front-ends, services, extensions, hook scripts, and capsules available. Taskwarrior keeps a list of contributed tools on their site.
Pro Lightweight and fast
Taskwarrior is written in the speedy C++ language.
Pro Tasks stored in plain text files locally
Future-proof and easily integrated with version control system. You never lose access to your data.

Pro Sync across devices
When used in conjunction with the Taskserver, it can sync tasks (conflict-free) across your Taskwarrior devices. This includes integration with Mirakel.

Pro Supported internationally
It has UTF8 support and is translated into many languages.
Pro Customizability
Taskworrior allows you to define custom attributes and reports to your needs.
Pro Self-hosted Taskserver
You can be in full control of your data.
Cons
Con Command line interface
A command line interface is a arguably overly verbose, consequently tedious, way to interact with a To Do list.
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