t9902: make test "set -e" clean

In order to catch mistakes like misspelling "test_expect_success",
we would like to eventually be able to run our test suite with the
"-e" option on.

This script uses the "read" utility to populate a single variable
with the contents of a here-document.  As "read" signals that it saw
the EOF by exiting with status 1, this triggers "set -e".

Here, we squelch it with the standard "|| :" trick.  A simpler
alternative may be to use a simpler assignment, e.g.,

    refs='main
    maint
    next
    seen'

Either way would work, but just honor the original author's
preference.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

t/t9902-completion.sh

@@ -590,7 +590,7 @@ test_expect_success '__gitcomp - doesnt fail because of invalid variable name' '
 	__gitcomp "$invalid_variable_name"
 '
 
-read -r -d "" refs <<-\EOF
+read -r -d "" refs <<-\EOF || :
 main
 maint
 next