merge: improve notes for listing the bids for ambiguous merges

merge: tell the user when we are using bid merge Bid merge is a new rarely used feature that the user explicitly enabled - we should tell/warn when the user actually is using it, just like we tell when we not are using it. Give a message like note: merging 3b08d01b0ab5+ and adfe50279922 using bids from ancestors 0f6b37dbe527 and 40663881a6dd

merge: fix stray character in bid merge message

tests: better test coverage for bid merge Martin Geisler's test case revealed the previous message argument error.

merge: fix wrong number of arguments for bid merge message

merge: fix test failures with new merge code on OS X The case collision checker was missing a op entry for 'k'eep.

obsolete: fix one-element tuple in module docstring

obsolete: let N denote number of obsoleted changestes in a marker The number of obsoleted changesets is referred to as N later in the docstring.

obsolete: fix language and grammar in module docstring

churn: compute padding with unicode strings Most UTF-8 aware terminals convert multibyte sequences into a single displayed characters. Because the first column is padded by counting bytes, the second column is not perfectly aligned in the presence of non ASCII characters.