Add shell completions for --env-file option

Adds completions for the --env-file toplevel option to the bash, fish,
and zsh completions files.

Signed-off-by: Klaas Hoekema <khoekema@azavea.com>

contrib/completion/bash/docker-compose

@@ -184,6 +184,10 @@ _docker_compose_docker_compose() {
 			_filedir -d
 			return
 			;;
+		--env-file)
+			_filedir
+			return
+			;;
 		$(__docker_compose_to_extglob "$daemon_options_with_args") )
 			return
 			;;
@@ -612,6 +616,7 @@ _docker_compose() {
 		--tlsverify
 	"
 	local daemon_options_with_args="
+		--env-file
 		--file -f
 		--host -H
 		--project-directory

contrib/completion/fish/docker-compose.fish

@@ -12,6 +12,7 @@ end
 
 complete -c docker-compose -s f -l file -r                -d 'Specify an alternate compose file'
 complete -c docker-compose -s p -l project-name -x        -d 'Specify an alternate project name'
+complete -c docker-compose -l env-file -r                 -d 'Specify an alternate environment file (default: .env)'
 complete -c docker-compose -l verbose                     -d 'Show more output'
 complete -c docker-compose -s H -l host -x                -d 'Daemon socket to connect to'
 complete -c docker-compose -l tls                         -d 'Use TLS; implied by --tlsverify'

contrib/completion/zsh/_docker-compose

@@ -341,6 +341,7 @@ _docker-compose() {
         '(- :)'{-h,--help}'[Get help]' \
         '*'{-f,--file}"[${file_description}]:file:_files -g '*.yml'" \
         '(-p --project-name)'{-p,--project-name}'[Specify an alternate project name (default: directory name)]:project name:' \
+        '--env-file[Specify an alternate environment file (default: .env)]:env-file:_files' \
         "--compatibility[If set, Compose will attempt to convert keys in v3 files to their non-Swarm equivalent]" \
         '(- :)'{-v,--version}'[Print version and exit]' \
         '--verbose[Show more output]' \
@@ -359,6 +360,7 @@ _docker-compose() {
     local -a relevant_compose_flags relevant_compose_repeatable_flags relevant_docker_flags compose_options docker_options
 
     relevant_compose_flags=(
+        "--env-file"
         "--file" "-f"
         "--host" "-H"
         "--project-name" "-p"