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

Author: scop

completions/Makefile.am

@@ -377,6 +377,7 @@ bashcomp_DATA = 2to3 \
 		_rtcwake \
 		_ruff \
 		_runuser \
+		_rustup \
 		sbcl \
 		sbopkg \
 		screen \

completions/_rustup

@@ -0,0 +1,17 @@
+# 3rd party completion loader for rustup                   -*- 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
+
+. <("$1" completions bash rustup 2>/dev/null)
+
+$_comp__load_3rdparty_reset_shopt
+
+{
+    complete -p "$1" || complete -p "${1##*/}"
+} &>/dev/null
+
+# ex: filetype=sh

test/fallback/completions/Makefile.am

@@ -25,6 +25,7 @@ EXTRA_DIST = \
 	rtcwake \
 	ruff \
 	runuser \
+	rustup \
 	slackpkg \
 	su \
 	svn \

test/fallback/completions/rustup

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