convert: use None value for missing files instead of overloading IOError The internal API used IOError to indicate that a file should be marked as removed. There is some correlation between IOError (especially with ENOENT) and files that should be removed, but using IOErrors to represent file removal internally required some hacks. Instead, use the value None to indicate that the file not is present. Before, spurious IO errors could cause commits that silently removed files. They will now be reported like all other IO errors so the root cause can be fixed.

merge with stable

convert: p4: ignore purged files with p4d 2012.2 and later Perforce has the concept of "+Sn" files where only the last revisions of the file is stored. In p4d 2012.1 old purged revisions were not included in the "manifest". With 2012.2 they started being included and convert's getfile failed to recognize the "purged" flag and saw it as an empty file. That made test-convert-p4-filetypes.t fail. There is no point in storing an empty file as placeholder for a purged file so we restore the old behaviour by checking the flag and letting getfile consider purged files deleted. (It is questionable whether it makes sense to convert not-yet-purged +S files to mercurial ... but that is another question.)