fix(bash): Fix bash completion for suggestions that contain special characters.

[JeffFaer]

Special characters include whitepace, so this is more general than
#1743. This should also fix #1740.

I added some test cases to cobra-completion-testing. This PR makes them
pass. It also doesn't trip any of the performance regression tests. I'm
happy to submit those tests as a PR as well.

• https://github.com/JeffFaer/cobra-completion-testing/tree/special_characters
• JeffFaer/cobra-completion-testing@52254c1

[CLAassistant]

All committers have signed the CLA.

[ncw]

It would be nice to have this PR merged - many rclone users have noticed that we can't complete file names with spaces in :-(

[marckhouzam]

Sorry for the delay. I will be reviewing this next.

[marckhouzam]

@JeffFaer

I'm happy to submit those tests as a PR as well.
https://github.com/JeffFaer/cobra-completion-testing/tree/special_characters
JeffFaer/cobra-completion-testing@52254c1

That would be great!

[JeffFaer]

marckhouzam/cobra-completion-testing#25

[marckhouzam]

I think there may be some confusion here.
When doing completion for special characters, the characters should be automatically escaped.
So if the completion choice is a>b, doing prog [tab][tab] should yield prog a\>b.
You can rebase #1743 and try it out as it behaves like this.
You can also try doing such completion with zsh and see how it should behave.