b4: add shell completion via python-shtab

The python-shtab module allows for static shell completion files, whereas others like python-argcomplete, execute the underlying tool for ever suggestion.

Currently it supports bash, zsh and tcsh - maintainer is open to patches supporting fish.

In addition, the action completion (aka is the argument is a folder, file, git sha, etc) is non-existing, but even as-is the completions are quite useful.

To generate/install the zsh completion use:
- ./b4.sh --print-completion zsh > _b4
- mv _b4 /usr/share/zsh/site-functions/_b4

For more details, see the website https://github.com/iterative/shtab

---
As with any tool, having shell completion is a must both to improve productivity and improve ramp-up for noobies.

Initially I started off writing zsh completion by hand, although the 100+ options quickly made me reconsider my life choices :-D

Instead we can use python-shtab, which:
- is an amazing starting point
- requires effectively zero maintenance by the b4 team

I have been using the zsh completion for a few weeks now and it works fine. From a quick test the bash completion is also quite decent.

If needed, the generated files can be checked into the git repo and expanded on. Even though personally I don't think that's a great idea.

Happy to do so, of course - let me know either way.

---
 src/b4/command.py | 7 +++++++
 1 file changed, 7 insertions(+)

index be0f033..10cb4d0 100644
@@ -363,6 +363,13 @@ def setup_parser() -> argparse.ArgumentParser:
                           help='Submit the token received via verification email')
     sp_send.set_defaults(func=cmd_send)
 
+    try:
+        import shtab
+
+        shtab.add_argument_to(parser, ["-s", "--print-completion"])
+    except ImportError:
+        pass
+
     return parser
 
 

---
base-commit: 7f3284906e67f138eae82271a6c3bde1ebb30791
change-id: 20240227-shell-completion-060a610f5b20

Best regards,

Emil Velikov <[email protected]>