dep/doc: add tab completion via argcomplete

[yunjunz]

Description of proposed changes

• add argcomplete to the dependency for tab completion capability, which is implemented in Single entrypoint with sub-commands #823 and described in Suggestions for MintPy #1041. This package is light (only depends on pure Python), and available on pip and conda-forge (as noarch package).

  • requirements.txt: add argcomplete
  • setup.py: move argcomplete from optional to required

• docs/installation.md: add "tab complete sub-commands" as another sub-section in Post-Installation Setup.

Reminders

• Pass Pre-commit check (green)
• Pass Codacy code review (green)
• Pass Circle CI test (green)
• If adding new functionality, add a detailed description to the documentation and/or an example.

[avalentino]

The changes are good to me.
Probably you may want to point out that, on Mac OSX, argcomplete >= 3.0 works perfectly on the default shell zsh. In that case no workaround is needed.

[falkamelung]

I was surprised that you can call mintpy functions using mintpy although there is no script/file called mintpy. Some explanation of why this works could be helpful.

[scottstanie]

I was surprised that you can call mintpy functions using mintpy although there is no script/file called mintpy. Some explanation of why this works could be helpful.

These come from the Mintpy entry points, which is the typical way a python package can make a command line tool available when you pip install the package (without messing with any $PYTHONPATH or $PATH environment variables). https://setuptools.pypa.io/en/latest/userguide/entry_point.html#console-scripts gives a minimal example to see how that works

[yunjunz]

I was surprised that you can call mintpy functions using mintpy although there is no script/file called mintpy. Some explanation of why this works could be helpful.

This nice feature was introduced in version 1.5.0 by @avalentino. It's very similar to the latest GMT. I have not advertised it heavily yet, as it may be confusing to users who are used to the view.py style.