test-lint: find unportable sed, echo, test, and export usage after &&

Instead of anchoring these checks with "^\s*", just check that the
usage is preceded by a word boundary.  So now we can catch

	test $cond && export foo=bar

just like we already catch

	test $cond &&
	export foo=bar

As a side effect, this will detect usage of "sed -i", "echo -n", "test
a == b", and "export a=b" in comments.  That is not ideal but it's
potentially useful because people sometimes copy code from comments so
it can be good to also avoid nonportable patterns there.

To avoid false positives, keep the checks for 'declare' and 'which'
anchored.  Those are frequently used words in normal English-language
comments.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/check-non-portable-shell.pl

@@ -16,12 +16,12 @@ sub err {
 
 while (<>) {
 	chomp;
-	/^\s*sed\s+-i/ and err 'sed -i is not portable';
+	/\bsed\s+-i/ and err 'sed -i is not portable';
-	/^\s*echo\s+-n/ and err 'echo -n is not portable (please use printf)';
+	/\becho\s+-n/ and err 'echo -n is not portable (please use printf)';
 	/^\s*declare\s+/ and err 'arrays/declare not portable';
 	/^\s*[^#]\s*which\s/ and err 'which is not portable (please use type)';
-	/test\s+[^=]*==/ and err '"test a == b" is not portable (please use =)';
+	/\btest\s+[^=]*==/ and err '"test a == b" is not portable (please use =)';
-	/^\s*export\s+[^=]*=/ and err '"export FOO=bar" is not portable (please use FOO=bar && export FOO)';
+	/\bexport\s+[A-Za-z0-9_]*=/ and err '"export FOO=bar" is not portable (please use FOO=bar && export FOO)';
 	# this resets our $. for each file
 	close ARGV if eof;
 }