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Syntax for identifying revisions
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There seem to be two main options: use a separate ``-r`` option, or
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put a revision identifier within the filename.
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``-r`` options are familiar from CVS and Subversion, and easy to
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specify, and cover almost all situations.
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Special identifiers in the filename are sometimes more concise, and
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allow for more complete specification of filenames in the presence of
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renames. They may be more complex to implement, and will cause some
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filenames to be either forbidden or to require escaping.
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How to interpret revisions in the presence of renamed files? Suppose
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hello.c was renamed in r3; when we do ``bzr diff -r2 hello.c`` should
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* the file currently called ``hello.c``, as it was in revision 2, even
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if it then had a different name
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* the file that was called ``hello.c`` in revision 2, even if that is
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Often only one will work, but it is possible to have situations where
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in revision 2 there was a file called ``hello.c`` but it is not the
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same one that now has that name.
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If we can have a simple syntax that accomodates either that would be
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good. One might be to mix revision numbers into the path, rather than
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a separate ``-r`` option. For example::
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The simplest case is to just append the number, but you can vary
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them. It might even be possible to chain them, getting the file id
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from one revision and its state from another:
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This means "the file that was called ``hello.c`` in revision 70, give
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me its state in revision 31." (If you wanted to do this across
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branches, I think you might need to get the file id and then look it
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Some more syntax: you can refer to a revision by its hash just by
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specifying that; we can distinguish them from anything else by their
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hello.c@09fac8dbfd27bd9b4d23a00eb648aa751789536d
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(Is that really safe? Perhaps some punctuation is needed to
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distinguish it from a label. But then I think people should rarely or
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never use them; perhaps it need not be allowed at all.)
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You can also give a date, which is used to find the most recent
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revision no later than that date::
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(Braces can be a bit scary for shell, but if there are no commas they
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Or, once we have labels, you can use a label::
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doc/revision-syntax.txt
