convert: add a mode where mercurial_sink skips empty revisions. The getchanges function of some converter_source classes can return some false positives. I.e. they sometimes claim that a file "foo" was changed in some revision, even though its contents are still the same. convert_svn is particularly bad, but I think this can also happen with convert_cvs and, at least in theory, with mercurial_source. For regular conversions this is not really a problem - as long as getfile returns the right contents, we'll get a converted revision with the right contents. But when we use --filemap, this could lead to superfluous revisions being converted. Instead of fixing every converter_source, I decided to change mercurial_sink to work around this problem. When --filemap is used, we're interested only in revisions that touch some specific files. If a revision doesn't change any of these files, then we're not interested in it (at least for revisions with a single parent; merges are special). For mercurial_sink, we abuse this property and rollback a commit if the manifest text hasn't changed. This avoids duplicating the logic from localrepo.filecommit to detect unchanged files.

     1

adding empty-file

     2

adding large-file

     3

adding another-file

     4

removing empty-file

     5

removing large-file

     6

recording removal of large-file as rename to another-file (99% similar)

     7

% comparing two empty files caused ZeroDivisionError in the past

     8

2 files updated, 0 files merged, 1 files removed, 0 files unresolved

     9

adding another-empty-file

    10

removing empty-file

    11

adding large-file

    12

adding tiny-file

    13

adding small-file

    14

removing large-file

    15

removing tiny-file

    16

recording removal of tiny-file as rename to small-file (82% similar)

    17

% should all fail

    18

abort: similarity must be a number

    19

abort: similarity must be between 0 and 100

    20

abort: similarity must be between 0 and 100