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.
header = '{date|shortdate} {author|person} <{author|email}>\n\n'
header_verbose = ''
changeset = '\t* {files|stringify|fill68|tabindent}{desc|fill68|tabindent|strip}\n\t[{node|short}]{tags}\n\n'
changeset_quiet = '\t* {desc|firstline|fill68|tabindent|strip}\n\n'
changeset_verbose = '{date|isodate} {author|person} <{author|email}> ({node|short}{tags})\n\n\t* {file_adds|stringify|fill68|tabindent}{file_dels|stringify|fill68|tabindent}{files|stringify|fill68|tabindent}{desc|fill68|tabindent|strip}\n\n'
start_tags = ' ['
tag = '{tag}, '
last_tag = '{tag}]'
file = '{file}, '
last_file = '{file}:\n\t'
file_add = '{file_add}, '
last_file_add = '{file_add}: new file.\n* '
file_del = '{file_del}, '
last_file_del = '{file_del}: deleted file.\n* '