check-code: allow "grep pattern filename-containing-dash-a"

We're trying to forbid "grep -a" and unintentionally complained even
if the "-a" was part of the filename. Requiring a space before "-a" to
match is probably good enough.

contrib/check-code.py

@@ -90,7 +90,7 b' testpats = ['
     (r'pushd|popd', "don't use 'pushd' or 'popd', use 'cd'"),
     (r'\W\$?\(\([^\)\n]*\)\)', "don't use (()) or $(()), use 'expr'"),
     (r'grep.*-q', "don't use 'grep -q', redirect to /dev/null"),
-    (r'(?<!hg )grep.*-a', "don't use 'grep -a', use in-line python"),
+    (r'(?<!hg )grep.* -a', "don't use 'grep -a', use in-line python"),
     (r'sed.*-i', "don't use 'sed -i', use a temporary file"),
     (r'\becho\b.*\\n', "don't use 'echo \\n', use printf"),
     (r'echo -n', "don't use 'echo -n', use printf"),