convert: handle closed branch heads in hg-hg conversion (issue2185)

check-code: add warning on lines over 80 characters

Remove variable output affected by length of TMPDIR. If the temporary directory is longer than /tmp then it's possible that the Subject line will get wrapped by the headencode function.

chunkbuffer: split big strings directly in chunkbuffer

localrepo.status: move fixup concatenation inside if block for clarity clean += fixup only makes sense if fixup is not empty; it should be inside the "if fixup" test.

chunkbuffer: targetsize isn't used outside of read()

chunkbuffer: use list instead of cStringIO

chunkbuffer: use for/else to detect end of iteration

changegroup*(): use enumerate when possible

changegroupsubset(): with the fix, prune() is actually useful in the testsuite