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.

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adding a

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# missing arg

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hg cat: invalid arguments

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hg cat [OPTION]... FILE...

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output the current or given revision of files

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    Print the specified files as they were at the given revision.

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    If no revision is given, the parent of the working directory is used,

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    or tip if no revision is checked out.

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    Output may be to a file, in which case the name of the file is

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    given using a format string.  The formatting rules are the same as

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    for the export command, with the following additions:

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    %s   basename of file being printed

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    %d   dirname of file being printed, or '.' if in repo root

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    %p   root-relative path name of file being printed

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options:

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 -o --output   print output to file with formatted name

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 -r --rev      print the given revision

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 -I --include  include names matching the given patterns

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 -X --exclude  exclude names matching the given patterns

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use "hg -v help cat" to show global options

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% [defaults]

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a

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a

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% no repo

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abort: There is no Mercurial repository here (.hg not found)!