autocomplete: fix instructions for enabling on Ubuntu 18.04 (bionic)

[dashohoxha]

The instructions for enabling shell autocompletion in bash are not complete (https://dvc.org/doc/user-guide/autocomplete). It only says:

On a current Linux OS (in a non-minimal installation), bash completion should be available;

This is true, but I also had to enable it by commenting out these lines on ~/.bashrc:

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

I am actually using LinuxMint 19, but it is based on Ubuntu 18.04, so this behavior should be the same for all the bionic systems (Ubuntu 18.04 and all the variations based on it).

[shcheklein]

@dashohoxha is there an official link that describes the process, so that we can just include it instead of duplicating this info?

[shcheklein]

@dashohoxha is it different from other systems? previous versions of Ubuntu? other Linux systems?

[dashohoxha]

is there an official link that describes the process, so that we can just include it instead of duplicating this info?

There are lots of blogs that describe it (for example this one: https://linuxhandbook.com/enable-tab-completion/), but no official docs that I am aware of, or that I could find.

is it different from other systems? previous versions of Ubuntu? other Linux systems?

I am not sure. The only safe way to find it out is to make a fresh installation of other versions/systems and to check it.
Some issues (like this one: https://ubuntuforums.org/showthread.php?t=2393044) may indicate that it has changed in the latest version of ubuntu, and it was enabled by default on previous versions. But it may also be that the user has enabled it on the previous version and forgot about it.

I have a raspbian system based on debian stretch, and it seems that there it is enabled by default. But I haven't checked it yet on debian buster. I will let you know about this later.

[shcheklein]

@dashohoxha yep, thanks for the research. It definitely makes sense to put a note with a link to some of these blogs or discussions if it's common across all new Ubuntus.

[dashohoxha]

I have a raspbian system based on debian stretch, and it seems that there it is enabled by default. But I haven't checked it yet on debian buster. I will let you know about this later.

It seems that bash autocomplete is enabled by default on debian buster as well, and also on ubuntu bionic etc. I don't know how I got the impression that it has to be enabled manually.
So, the current documentation is correct, after all. Sorry for the confusion.

Sometimes it may not be working out of the box (for different reasons), and knowing how to fix it manually can be useful. To cover this case we can add a expanding note with a link to this blog: https://linuxhandbook.com/enable-tab-completion/ It seems to be a stable blog site and if ever it disappears, some users may notice and report it, and we can switch to some other blog post.

Can I add this note on the page?

[shcheklein]

@dashohoxha absolutely! a note with a brief comment can be useful and save some people time.