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

https://github.com/jaraco/keyring#tab-completion

Author: scop

completions/Makefile.am

@@ -210,6 +210,7 @@ bashcomp_DATA = 2to3 \
 		jsonschema \
 		k3b \
 		kcov \
+		_keyring \
 		kill \
 		killall \
 		kldload \

completions/_keyring

@@ -0,0 +1,9 @@
+# 3rd party completion loader for commands emitting        -*- shell-script -*-
+# their completion using "$cmd --print-completion bash".
+# For example, many Python programs using https://github.com/iterative/shtab do.
+#
+# This serves as a fallback in case the completion is not installed otherwise.
+
+eval -- "$("$1" --print-completion bash 2>/dev/null)"
+
+# ex: filetype=sh

test/fallback/completions/Makefile.am

@@ -14,6 +14,7 @@ EXTRA_DIST = \
 	hexdump \
 	hwclock \
 	ionice \
+	keyring \
 	look \
 	mdbook \
 	mock \

test/fallback/completions/keyring

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