Narrow lint target to just the drafts

[martinthomson]

Note that this doesn't filter out non-markdown drafts, so this will fail in the general case, but I don't think that we'll have that problem here.

Fixes martinthomson/i-d-template#143 for @MikeBishop. I hope.

[MikeBishop]

<Non-breaking change to doc>
mbishop@sea-wpwin:~/github/quic$ git add draft-ietf-quic-qpack.md
<Breaking change to doc>
mbishop@sea-wpwin:~/github/quic$ git status
On branch narrow-lint
Your branch is up-to-date with 'origin/narrow-lint'.
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        modified:   draft-ietf-quic-qpack.md

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   draft-ietf-quic-qpack.md

mbishop@sea-wpwin:~/github/quic$ git commit -m "DO NOT PUSH"
cat draft-ietf-quic-qpack.md | sed -e 's/{DATE}/2018-05-15/g'  | kramdown-rfc2629 > draft-ietf-quic-qpack.xml
** Configuration problem with OpenSSL certificate store at /usr/lib/ssl/cert.pem.
**   Activating workaround.  Occasionally run `certified-update`.
xml2rfc -q draft-ietf-quic-qpack.xml -o draft-ietf-quic-qpack.txt --text
115: Line is 104 characters; limit is 80
and can always be processed immediately. Innocuous change.Overrunning the end of the line intentionally.
Makefile:25: recipe for target 'lint' failed
make: *** [lint] Error 1
rm draft-ietf-quic-qpack.xml
Commit refused: documents don't build successfully.
To commit anyway, run "git commit --no-verify"
mbishop@sea-wpwin:~/github/quic$

No, it still seems to be running lint/building the documents in the directory rather than just the ones staged.

[martinthomson]

I see. I think that this is an easy fix, but we'll see. We would still need this change, but also some more changes on the template. In progress....

[martinthomson]

@MikeBishop retry please.

[MikeBishop]

Yep, works now. Thank you!