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.
abort: file .../test-symlink-basic/a/dangling not tracked!
changeset: 0:cabd88b706fc
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: dangling
description:
add symlink
2564acbe54bbbedfbf608479340b359f04597f80 644 dangling
% rev 0:
dangling -> nothing
% rev 1:
dangling -> void
% modifying link
dangling -> empty
% reverting to rev 0:
reverting dangling
dangling -> nothing
% backups:
dangling.orig -> empty
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% copies
copying dangling to dangling2
A dangling2
dangling
dangling -> void
dangling2 -> void