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

https://github.com/iterative/shtab/blob/b83be0581c6cbd46d17b70b7faf235b2e0ba359e/shtab/main.py#L29

Author: scop

completions/Makefile.am

@@ -404,6 +404,7 @@ cross_platform = 2to3 \
 		sh \
 		sha256sum \
 		shellcheck \
+		_shtab \
 		sitecopy \
 		slabtop \
 		_slackpkg \

completions/_shtab

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

test/fallback/completions/shtab

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

test/t/Makefile.am

@@ -568,6 +568,7 @@ EXTRA_DIST = \
 	test_sha512sum.py \
 	test_shar.py \
 	test_shellcheck.py \
+	test_shtab.py \
 	test_sitecopy.py \
 	test_slabtop.py \
 	test_slackpkg.py \

test/t/test_shtab.py

@@ -0,0 +1,11 @@
+import pytest
+
+
+class TestShtab:
+    @pytest.mark.complete("shtab ", require_cmd=True)
+    def test_basic(self, completion):
+        assert not completion
+
+    @pytest.mark.complete("shtab -", require_cmd=True)
+    def test_options(self, completion):
+        assert completion

test/test-cmd-list.txt

@@ -346,6 +346,7 @@ sha384sum
 sha512sum
 shar
 shellcheck
+shtab
 sitecopy
 slabtop
 slapt-get