contrib: add an utility module to parse test scripts This patch centralizes the logic to pick up code fragments embedded in *.t script, in order to: - apply checking with patterns in check-code.py on such embedded code fragments Now, check-code.py completely ignores embedded code fragments. I'll post another patch series to check them. - replace similar code path in contrib/import-checker.py Current import-checker.py has problems below. Fixing each of them is a little difficult, because parsing logic and pattern strings are tightly coupled. - overlook (or mis-detect) the end of inline script in doctest style 8a8dd6e4a97a fixed a part of this issue, but not enough. - it overlooks inline script in doctest style at the end of file (and ignores invalid un-closed heredoc at the end of file, too) - it overlooks code fragment in styles below - "python <<EOF" (heredoc should be "cat > file <<EOF" style) - "cat > foobar.py << ANYLIMIT" (limit mark should be "EOF") - "cat << EOF > foobar.py" (filename should be placed before limit mark) - "cat >> foobar.py << EOF" (appending is ignored) - it is not extensible for other than python code fragments (e.g. shell script, hgrc file, and so on) This new module can detect python code fragments in styles below: - inline script in doctest style (starting by " >>> " line) - python invocation with heredoc script ("python <<EOF") - python script in heredoc style (redirected into ".py" file) As an example of extensibility of new module, this patch also contains implementation to pick up code fragment below. This will be useful to add additional restriction for them, for example. - shell script in heredoc style (redirected into ".sh" file) - hgrc configuration in heredoc style (redirected into hgrc or $HGRCPATH)