windows: don’t set `softspace` attribute in `winstdout` Python 2 file objects have the `softspace` attribute (https://docs.python.org/2/library/stdtypes.html#file.softspace), which is used by the print statement to track its internal state. The documentation demands from file-like objects only that the attribute is writable and initialized to 0. Method `file.write()` sets it to 0, but this is not documented. Historically, sys.stdout was replaced by an instance of the `winstdout` class, so it needed to behave exactly the same (the softspace fix was introduced in 705278e70457). Nowadays we don’t replace sys.stdout and don’t use the print statement on `winstdout` instances, so we can safely drop it.

windows: handle file-like objects without isatty() method Copying the function is not nice, but moving around stuff to avoid the circular import didn’t seem to be worth the effort.

exchange: check actually missing revs for obsolete / unstable revs (issue6372) The previous code was using `outgoing.ancestorsof`, which was originally called `outgoing.missingheads` although not containing the missing heads. This confusion was probably the reason why the buggy code was written. The actually outgoing changesets are stored in `outgoing.missing`. By checking all outgoing changesets, we avoid the problem and can show the list of all obsolete or unstable changesets, which is more helpful for the user.

tests: test that push doesn’t complain about unstable changesets if no changes When there’re no outgoing changes, push doesn’t complain about unstable changesets. There is currently a bug (see issue6372) that causes that there is an abort on push when the outgoing changes contain another changeset even if that is not obsolete or unstable. A test case and fix for that is sent in the next patch.

diff: move no-eol text constant to a common location Differential Revision: https://phab.mercurial-scm.org/D8763

revert: fix interactive reverting of end-of-file newline changes The chunk reversal used by `revert -i` in Curses mode was not taking this case into account. Differential Revision: https://phab.mercurial-scm.org/D8762