contributing: improve description.. description
This factors the finer details out of the broad description spec, moving
them into the next paragraph.
@@ -54,16 +54,17 @@ others.
Commits should generally be relevant, atomic, and have descriptions formatted
in the following manner:
-> component: short description (<= 50 characters total)
+> component: short description
>
-> long description (optional)
+> long description
The 'component' is a short prefix of what area of the codebase the commit
applies to. If a commit patches `%gall`, for example, the description should
be prefixed by 'gall'. If it touches `:aqua`, it should be prefixed by 'aqua'.
If it touches multiple components, then separate these by commas, e.g. "gall,
aqua, ph" -- but note that this may be a warning that too many changes are
-being packed into a single commit.
+being packed into a single commit. The 'component' and 'short description'
+combined should be no more than 50 characters.
A lengthier description is encouraged, where useful, but is not required.
