Add a bit of documentation about the upcoming GH_TUPLE.

[wblock]

en_US.ISO8859-1/books/porters-handbook/makefiles/chapter.xml

1986

Split the sentence rather than use a comma:

...into one variable.  The format is

1988

This should use <replaceable> on the non-literal parts. There is an <optional> tag for optional components. So (untested):

<replaceable>account</replaceable><literal>:</literal><replaceable>project</replaceable><literal>:</literal><replaceable>tagname</replaceable><optional><literal>:</literal><replaceable>group</replaceable></optional>

This really could use an example. Two, maybe, one with the optional group.

1989

s/are/is/

1990

Purists would suggest "from which to fetch."

2091

No comma needed.

2092

Split the sentence here, and "all" is not needed:

are a lot of distribution files.  It helps keep the

2164

Not quite clear what this means. Is it "This is the same as the previous example, but```?

2180

This sentence is also a little confusing. Maybe:

Grouping was used in the previous example with <literal>bar:icons,contrib</literal>.
Some redundant information is present with <varname>GH_TUPLE</varname> because
grouping is not possible.

[mat]

en_US.ISO8859-1/books/porters-handbook/makefiles/chapter.xml

1988

That gets:

element optional: validity error : Element literal is not declared in optional list of possible children

If I wrap all inside a <literal>, I get:

element literal: validity error : Element optional is not declared in literal list of possible children

I will drop the optional part and make it not optional, as we don't want people using it without the :group. bit.