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.
The last line of a non newline-terminated file would mix with the first line of
the next file in multiple-file listings before this patch.
Possible compatibility issue: no longer possible to tell from the annotate
output if the file is terminated by new line or not.
splitblock() was added to handle blocks returned by bdiff.blocks() which differ
only by blank lines but are not made only of blank lines. I do not know exactly
how it could happen but mdiff.blocks() threshold behaviour makes me think it
can if those blocks are made of very popular lines mixed with popular blank
lines. If it is proven to be wrong, the function can be dropped.
The first implementation made annotate share diff configuration entries. But it
looks like users will user -w/b for annotate but not for diff, on both the
command line and hgweb. Since the latter cannot use command line entries, we
introduce a new [annotate] section duplicating the diff whitespace options.
