Re: Bash completion for git aliases containing nested subcommands

> On Mon, Oct 03, 2022 at 11:45:51AM +0000, Tim Jaacks wrote:
>> Hello everyone,
>>
>> I have set up the following alias in my .gitconfig file:
>>
>> [alias]
>> ss = stash show
>>
>> Unfortunately bash completion does not work correctly on this alias. When I
>> type "git ss <TAB>", I get:
>>
>> $ git ss <TAB>
>> apply clear drop pop show
>> branch create list push
>>
>> Which is obviously the completion for "git stash" instead of "git stash
>> show".
>>
>> With the original command I get the list of available stashes:
>>
>> $ git stash show <TAB>
>> stash@{0} stash@{1}
>>
>> Is there a way to get the completion on the alias behave like on the
>> original command?
>
> In general: no.  Our Bash completion script is organized as one
> _git_cmd() function for each git supported command.  If a command has
> subcommands, then its completion function looks for any of its
> subcommands amond the words on the command line, and takes the
> appropriate action, which is usually executing a particular arm of a
> case statement.  The two main issues are that in case of such an alias
> there is no subcommand ("show") on the command line, and there is no
> dedicated function to handle only the completion for 'git stash show'.
>
> However, it is possible to make completion work for your particular
> alias by using our completion script's extension mechanism that allows
> users to specify completion functions to their own git commands.  If
> you type 'git foo <TAB>' and there is a _git_foo() function in your
> shell's environment, then the completion script will invoke that
> function to perform completion; this works not only for commands but
> for aliases as well.  So for your alias you only need to "borrow" all
> the "show"-subcommand-specific case arms from _git_stash() and place
> them in a _git_ss() function, e.g. like this:
>
> _git_ss () {
> case "$cur" in
> --*)
> __gitcomp_builtin stash_show "$__git_diff_common_options"
> ;;
> *)
> __gitcomp_nl "$(__git stash list | sed -n -e 's/:.*//p')"
> ;;
> esac
> }
>
> Add it to your ~/.bashrc, or to a separate file that you source from
> your .bashrc;  If you use bash-completion, then you don't even have to
> touch you .bashrc: save that function to a file 'git-ss' (dash, not
> underscore!) in one of the directories scanned by bash-completion
> ($BASH_COMPLETION_USER_DIR, ~/.local/share/bash-completion/completions
> or its XDG_DATA_HOME-equivalent) and it will be auto-loaded as needed.
>
> This approach should work just as well for any other similar "command
> subcommand" alias that you might have; with the downside that you'll
> have to write all these functions yourself.
>
>> I am on Ubuntu 20.04 and using the distro's default git completions.
>>
>> Kind regards,
>> Tim