Export options are now bundled into their own struct.

All regression tests pass.
More uniform naming.
Blob generation finally moves into export_commits().

All regression tests pass.
Cleanup after the refactoring.  All regression tests pass.
Update hacking.asc to match the recent refactoring.
Pass the export-options srreucture all the way down to export_commit().

All regression tests pass.
Fold another option completely into export_revisions.

All regression tests pass.
Cleanup: close a file in the same context where it's opened.

All regression tesrs pass.
Fast mode is documented, but only half implemented.

Blobs don't have marks, and the branchorder code seems to have bitrotted.

All regression tests pass (in the default canonical mode).
Another step towards fast mode (mot yet working).

All regression tests pass.
Cleanup.  All regression tests pass.
Don't creare a temp directory we won't use in fast mode.

All regression tests pass.
This looks like it might do fast mode correctly. All regression tests pass.
Re-enable and improve progress reporting.

All regressuin tests pass.
Beginning test production for fast-mode compatibility check.
Fast mode seems to be working...

...but my attempt to build  regression check for it failed die to some
nondeterminism omn how git-fast-export dumps branch repos.  It seems to picl
the first branch to dump at random.

All regression tests pass.
Sigh, at least we can test the linear case repeatably.