Merge pull request #1804 from NoahGorny/cleanup/docker-completions

completion: Lint docker completion and add about-completion

clean_files.txt

@@ -62,6 +62,7 @@ completion/available/brew.completion.bash
 completion/available/cargo.completion.bash
 completion/available/conda.completion.bash
 completion/available/consul.completion.bash
+completion/available/docker.completion.bash
 completion/available/knife.completion.bash
 completion/available/packer.completion.bash
 completion/available/pipx.completion.bash

completion/available/docker.completion.bash

@@ -1,10 +1,12 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+cite "about-completion"
+about-completion "docker completion"
 
 # Make sure docker is installed
 _command_exists docker || return
 
 # Don't handle completion if it's already managed
-complete -p docker &>/dev/null && return
+_completion_exists docker && return
 
 _docker_bash_completion_paths=(
 	# MacOS
@@ -15,6 +17,7 @@ _docker_bash_completion_paths=(
 
 for fn in "${_docker_bash_completion_paths[@]}"; do
 	if [ -r "$fn" ]; then
+		# shellcheck disable=SC1090
 		source "$fn"
 		break
 	fi