Add a Bash completion script for the Godot editor

Created by: Calinou

Follow-up to #34957.

In a future pull request, the zsh completion could be updated to support features only available in the Bash completion, such as contextual extension-based file name filtering.

Props to this article for explaining how to write Bash completion scripts 🙂

Preview

List of options

[user@host ~]$ godot --[TAB]
--always-on-top                 --export-pack                   --project-manager
--audio-driver                  --fixed-fps                     --quiet
--breakpoints                   --frame-delay                   --quit
--build-solutions               --fullscreen                    --remote-debug
--check-only                    --gdnative-generate-json-api    --remote-fs
--debug                         --help                          --remote-fs-password
--debug-collisions              --language                      --render-thread
--debug-navigation              --low-dpi                       --resolution
--disable-crash-handler         --main-pack                     --script
--disable-render-loop           --maximized                     --test
--disable-vsync-via-compositor  --no-docbase                    --time-scale
--doctool                       --no-window                     --upwards
--editor                        --path                          --verbose
--enable-vsync-via-compositor   --position                      --version
--export                        --print-fps                     --video-driver
--export-debug                  --profiling                     --windowed

Option completion

[user@host ~]$ godot --video-driver [TAB]
GLES2  GLES3

Positional argument completion

[user@host some_project]$ godot [TAB]
scene.scn  project.godot        test.tscn