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.
changeset: 3:593cbf6fb2b4
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added tag some-tag for changeset ad681a868e44
changeset: 2:ad681a868e44
tag: some-tag
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo/file
changeset: 1:cbba8ecc03b7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: remove foo
changeset: 0:327daa9251fa
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo and bar
initializing destination new repository
scanning source...
sorting...
converting...
3 add foo and bar
2 remove foo
1 add foo/file
0 Added tag some-tag for changeset ad681a868e44
comparing with ../orig
searching for changes
no changes found
% dirstate should be empty:
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
% put something in the dirstate:
a 0 -1 unset baz
copy: bar -> baz
% add a new revision in the original repo
destination new is a Mercurial repository
scanning source...
sorting...
converting...
0 add baz
comparing with ../orig
searching for changes
no changes found
% dirstate should be the same (no output below):
% no copies
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
baz not renamed