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.
# mq patch on an empty repo
tip: 0
No .hg/branch.cache
tip: 0
No .hg/branch.cache
# some regular revisions
Patch queue now empty
tip: 1
3f910abad313ff802d3a23a7529433872df9b3ae 1
3f910abad313ff802d3a23a7529433872df9b3ae bar
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo
# add some mq patches
applying p1
Now at: p1
tip: 2
3f910abad313ff802d3a23a7529433872df9b3ae 1
3f910abad313ff802d3a23a7529433872df9b3ae bar
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo
tip: 3
3f910abad313ff802d3a23a7529433872df9b3ae 1
3f910abad313ff802d3a23a7529433872df9b3ae bar
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo
branch foo: 3
branch bar: 2
# removing the cache
tip: 3
3f910abad313ff802d3a23a7529433872df9b3ae 1
3f910abad313ff802d3a23a7529433872df9b3ae bar
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo
branch foo: 3
branch bar: 2
# importing rev 1 (the cache now ends in one of the patches)
tip: 3
3f910abad313ff802d3a23a7529433872df9b3ae 1
3f910abad313ff802d3a23a7529433872df9b3ae bar
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo
branch foo: 3
branch bar: 2
qbase: 1
# detect an invalid cache
Patch queue now empty
applying p0
applying p1
applying p2
Now at: p2
tip: 3
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff 0
9539f35bdc80732cc9a3f84e46508f1ed1ec8cff foo