Meta: improve pull request guidelines

Fixes #276.

Author: annevk

README.md

@@ -15,11 +15,68 @@ started, leave a comment on the issue or ask around [on IRC](https://wiki.whatwg
 
 ### Pull requests
 
-See the [html repository's README](https://github.com/whatwg/html/blob/master/README.md) for the
-general guidelines. Note that `source` is `Overview.src.html` and "Acknowledgements" is
-"Acknowledgments" here (I know). Also, the Fetch Standard uses
-[Anolis](https://wiki.whatwg.org/wiki/Anolis) to generate `Overview.html`. (Do not worry if using
-that tool is too complicated, your pull request does not need to contain the generated HTML.)
+In short, change `Overview.src.html` and submit your patch, with a
+[good commit message](https://github.com/erlang/otp/wiki/Writing-good-commit-messages). Consider
+reading through the [WHATWG FAQ](https://wiki.whatwg.org/wiki/FAQ) if you are new here.
+
+Please add your name to the Acknowledgments section in your first pull request, even for trivial
+fixes. The names are sorted lexicographically.
+
+To generate `Overview.html`, [Anolis](https://wiki.whatwg.org/wiki/Anolis) can be used. (Do not
+worry if using that tool is too complicated, your pull request does not need to contain the
+generated HTML to be accepted.)
+
+#### Formatting
+
+Use a column width of 100 characters.
+
+Do not use newlines inside "inline" elements, even if that means exceeding the column width
+requirement.
+```html
+ <li><p>Execute
+ <a href=https://w3c.github.io/webappsec-csp/#set-response-csp-list>set <var>response</var>'s CSP list</a>
+ on <var>response</var>. <span data-anolis-ref>CSP</span>
+```
+is okay and
+  ```html
+ <li><p>Execute
+ <a href=https://w3c.github.io/webappsec-csp/#set-response-csp-list>set <var>response</var>'s CSP
+ list</a> on <var>response</var>. <span data-anolis-ref>CSP</span>
+```
+is not.
+
+Using newlines between "inline" element tag names and their content is also forbidden. (This
+actually alters the content, by adding spaces.) That is
+```html
+<a>token</a>
+```
+is fine and
+```html
+<a>token
+</a>
+```
+is not.
+
+An `<li>` element always has a `<p>` element inside it, unless it's a child of `<ul class=brief>`.
+
+If a "block" element contains a single "block" element, do not put it on a newline.
+
+Do not indent for anything except a new "block" element. For instance
+```html
+ <li><p>Set <var>response</var>'s <span title=concept-response-url-list>url list</span> to a copy of
+ <var>request</var>'s <span title=concept-request-url-list>url list</span>.
+```
+is not indented, but
+```html
+ <li>
+  <p>Run these substeps <span data-anolis-spec=html>in parallel</span>:
+
+  <ol>
+```
+is.
+
+End tags must be omitted when possible and attribute values must not be quoted (if necessary, use
+double quotes).
 
 ### Merge policy