tests/test-gendoc.t

fix: highlight the required configuration and behavior of the fixer tools

The problem is that `hg help fix` didn't mention *how* to configure the tools,
and while I knew that `{rootpath}` existed in the configuration, I missed that
the tools require reading content from stdin.  (I configured `gofmt` to use
`{rootpath}`, and that had the effect of squashing all changes in a file at `.`
into the first commit and emptying that content from its descendants.)

Basically all this does is put a pointer in the default (command level) help to
the extension level help that mentions the configuration, and moves the
extension level help that documents reading from stdin and writing to stdout to
the top to give it more prominence.  The last sentence is adjusted a bit to
reflect the new location.

#require docutils
#require gettext

Test document extraction

  $ HGENCODING=UTF-8
  $ export HGENCODING
  $ { echo C; ls "$TESTDIR/../i18n"/*.po | sort; } | while read PO; do
  >     LOCALE=`basename "$PO" .po`
  >     echo "% extracting documentation from $LOCALE"
  >     LANGUAGE=$LOCALE "$PYTHON" "$TESTDIR/../doc/gendoc.py" >> gendoc-$LOCALE.txt 2> /dev/null || exit
  > 
  >     if [ $LOCALE != C ]; then
  >         if [ ! -f $TESTDIR/test-gendoc-$LOCALE.t ]; then
  >             echo missing test-gendoc-$LOCALE.t
  >         fi
  >         cmp -s gendoc-C.txt gendoc-$LOCALE.txt && echo "** NOTHING TRANSLATED ($LOCALE) **"
  >     fi
  > done; true
  % extracting documentation from C
  % extracting documentation from da
  % extracting documentation from de
  % extracting documentation from el
  % extracting documentation from fr
  % extracting documentation from it
  % extracting documentation from ja
  % extracting documentation from pt_BR
  % extracting documentation from ro
  % extracting documentation from ru
  % extracting documentation from sv
  % extracting documentation from zh_CN
  % extracting documentation from zh_TW