incremental imports from incremental input streams

[Matt McClure]

I'd like to use bzr fast-import to sync a Bazaar branch from Perforce.
 It works if I do full exports from Perforce, but that doesn't scale
very well. Instead I'd like to do incremental migrations. Some
avenues I've explored include:

* fast-import's BadRestart validation

* fast-import's --import-marks option

* the 'from' command specified in the git fast-import documentation

Fast-import's BadRestart validation prevents importing, for example,
revision 3 by itself, to a repository that contains revisions 1 and 2.

Fast-import's --import-marks option raises KeyError if the incremental
import contains no overlapping revisions, e.g., revision 3 to a
repository containing revisions 1 and 2. On the other hand, if the
incremental import does contain overlapping revisions, e.g. revisions
2 and 3 to a repository containing revisions 1 and 2, then fast-import
creates a duplicate revision in the Bazaar branch for revision 2.

From the documentation, it sounds like the 'from' command in the
stream is what I want, but it looks like bzr fast-import doesn't
support it.

To the fast-import folks, how would you recommend I proceed?

Thanks,
Matt

[Robert Collins (lifeless)]

Here is another usecase - Ian, please say if this should be a new bug:

User has a git repository that has a tree which is 'close enough' to some known revision in a bzr repository; they want to take the commits done on top of that tree in git, and import them to bzr. bzr-git is unsuitable - the bzr repository is not converted from git in the first place.

Something like 'git fast-export <last 5 commits> | bzr fast-import --append' would be one way to express this (where the bzr branch has been uncommitted or whatever to be a 'close enough' fit to the matching git tree.