Re: [PATCH 1/1] fast-import: checkpoint: dump branches/tags/marks even if object_count==0

> The checkpoint command cycles packfiles if object_count != 0, a sensible
> test or there would be no pack files to write. Since 820b931012, the
> command also dumps branches, tags and marks, but still conditionally.
> However, it is possible for a command stream to modify refs or create
> marks without creating any new objects.
> 
> For example, reset a branch (and keep fast-import running):
> 
> 	$ git fast-import
> 	reset refs/heads/master
> 	from refs/heads/master^
> 
> 	checkpoint
> 
> but refs/heads/master remains unchanged.
> 
> Other example: a commit command that re-creates an object that already
> exists in the object database.
> 
> The man page also states that checkpoint "updates the refs" and that
> "placing a progress command immediately after a checkpoint will inform
> the reader when the checkpoint has been completed and it can safely
> access the refs that fast-import updated". This wasn't always true
> without this patch.
> 
> This fix unconditionally calls dump_{branches,tags,marks}() for all
> checkpoint commands. dump_branches() and dump_tags() are cheap to call
> in the case of a no-op.
> 
> Add tests to t9300 that observe the (non-packfiles) effects of
> checkpoint.
> 
> Signed-off-by: Eric Rannaud <e@nanocritical.com>
> ---
>  fast-import.c          |   6 +--
>  t/t9300-fast-import.sh | 126 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 129 insertions(+), 3 deletions(-)
> 
> 
> Updated to include Junio's latest remarks.
> 
> Also adding the necessary PIPE prereq, as pointed out by Ramsay Jones.