feat(cargo): add fallback 3rd party completion loader

Author: scop

completions/Makefile.am

@@ -38,6 +38,7 @@ bashcomp_DATA = 2to3 \
 		bzip2 \
 		_cal \
 		cancel \
+		_cargo \
 		cardctl \
 		carton \
 		ccache \

completions/_cargo

@@ -0,0 +1,18 @@
+# 3rd party completion loader for cargo                    -*- shell-script -*-
+#
+# This serves as a fallback in case the completion is not installed otherwise.
+
+# shellcheck disable=SC2168 # "local" is ok, assume sourced by __load_completion
+local _comp__load_3rdparty_reset_shopt=$(shopt -po posix)
+set +o posix
+
+local rustup="${1%cargo}rustup" # use rustup from same dir
+. <("$rustup" completions bash cargo 2>/dev/null)
+
+$_comp__load_3rdparty_reset_shopt
+
+{
+    complete -p "$1" || complete -p "${1##*/}"
+} &>/dev/null
+
+# ex: filetype=sh

test/fallback/completions/Makefile.am

@@ -1,6 +1,7 @@
 EXTRA_DIST = \
 	adb \
 	cal \
+	cargo \
 	chfn \
 	chsh \
 	dmesg \

test/fallback/completions/cargo

@@ -0,0 +1 @@
+../../../completions/_cargo