mergestate: document mergestate records in an organized way This makes clear which mergestate record is used for what and group them based on how they are used right now. Differential Revision: https://phab.mercurial-scm.org/D8719

mergestate: remove unused unsupported related mergestate records I tried to find users of this but was unable to find. Seems like RECORD_OVERRIDE is doing for what they were used before. Differential Revision: https://phab.mercurial-scm.org/D8718

mergestate: add comments about couple of record types and minor reorder I am trying to divide the records into certain groups and then have dedicated objects for them. Taking baby steps in that direction. Differential Revision: https://phab.mercurial-scm.org/D8717

mergestate: remove unrequired RECORD_RESOLVED_OTHER record This was introduced in last cycle however while working on refactoring mergestate, I realized it's unncessary. This will break users who did a merge using previous version, did this kind of storage and before commiting updated the mercurial version. Differential Revision: https://phab.mercurial-scm.org/D8716

mergestate: rename addpath() -> addpathonflict() to prevent confusion addpath() seems to imply that we are adding a new path/entry to the mergestate. Differential Revision: https://phab.mercurial-scm.org/D8715

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.