[PATCH 4/7] completion: add tests for invalid variable name among completion words

["SZEDER Gábor" <szeder@ira.uka.de>]

The compgen Bash-builtin performs expansion on all words in the
wordlist given to its -W option, breaking Git's completion script in
various ways if one of those words can be expanded.  The breakage can
be simply bogus possible completion words, but it can also be a
failure:

  $ git branch '${foo.bar}'
  $ git checkout <TAB>
  bash: ${foo.bar}: bad substitution

${foo.bar} is an invalid variable name, which triggers the failure
when compgen attempts to expand it, completely breaking refs
completion.  The same applies to e.g. completing the <tree>:<path>
notation when a filename contains a similar expandable substring.

Since both __gitcomp() and __gitcomp_nl() rely on compgen, both are
affected by this issue.  So add a simple test for each of them to
check that such a word doesn't cause failures (but don't check the
resulting possible completion words for now, because that should be
quoted properly, and that's a separate topic).

Reported-by: Jeroen Meijer <jjgmeijer@hotmail.com>
Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
---
 t/t9902-completion.sh | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 32b3e8c4..a108ec1c 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -71,6 +71,7 @@ test_completion_long ()
 }
 
 newline=$'\n'
+invalid_variable_name="${foo.bar}"
 
 test_expect_success '__gitcomp - trailing space - options' '
 	sed -e "s/Z$//" >expected <<-\EOF &&
@@ -155,6 +156,12 @@ test_expect_success '__gitcomp - suffix' '
 	test_cmp expected out
 '
 
+test_expect_failure '__gitcomp - doesnt fail because of invalid variable name' '
+	(
+		__gitcomp "$invalid_variable_name"
+	)
+'
+
 test_expect_success '__gitcomp_nl - trailing space' '
 	sed -e "s/Z$//" >expected <<-\EOF &&
 	maint Z
@@ -239,6 +246,12 @@ test_expect_success '__gitcomp_nl - no suffix' '
 	test_cmp expected out
 '
 
+test_expect_failure '__gitcomp_nl - doesnt fail because of invalid variable name' '
+	(
+		__gitcomp_nl "$invalid_variable_name"
+	)
+'
+
 test_expect_success 'basic' '
 	run_completion git "" &&
 	# built-in
-- 
1.8.0.220.g4d14ece