nodemap: update the index with the newly written data (when appropriate)
If we are to use mmap to read the nodemap data, and if the python code is
responsible for the IO, we need to refresh the mmap after each write and provide
it back to the index.
We start this dance without the mmap first.
Differential Revision: https://phab.mercurial-scm.org/D7893
#require docutils gettext
$ $TESTDIR/check-gendoc de
checking for parse errors
Die Dateien werden dem Projektarchiv beim n\xc3\xa4chsten \xc3\x9cbernehmen (commit) hinzugef\xc3\xbcgt. Um dies vorher r\xc3\xbcckg\xc3\xa4ngig zu machen, siehe:hg:`forget`. (esc)
warning: please have a space before :hg: