Many tests didn't change back from subdirectories at the end of the tests ...
and they don't have to. The missing 'cd ..' could always be added when another
test case is added to the test file.
This change do that tests (99.5%) consistently end up in $TESTDIR where they
started, thus making it simpler to extend them or move them around.
Overwriting instead of appending to the file removes the [defaults]
section put into the file by run-tests.py.
It also defeats the --inotify option to run-tests.py.
(Nothing was broken yet, but the lack of -d "0 0" cause changeset
hashes to change unexpectedly in a test case I was editing.)
When issuing `hg pull -r REV` in a repo with no common ancestor with the
remote repo, the message 'requesting all changes' is printed, even though only
the changese that are ancestors of REV are actually requested. This can be
confusing for users (see
http://www.selenic.com/pipermail/mercurial/2010-October/035508.html).
This silences the message if (and only if) the '-r' option was passed.
