Re: [PATCH] Add 'git fast-export', the sister of 'git fast-import'

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Sun, 25 Nov 2007, Junio C Hamano wrote:

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > diff --git a/Documentation/git-fast-export.txt b/Documentation/git-fast-export.txt
> > new file mode 100644
> > index 0000000..073ff7f
> > --- /dev/null
> > +++ b/Documentation/git-fast-export.txt
> > ...
> > +DESCRIPTION
> > +-----------
> > +This program dumps the given revisions in a form suitable to be piped
> > +into gitlink:git-fast-import[1].
> > +
> > +You can use it as a human readable bundle replacement (see
> > +gitlink:git-bundle[1]), or as a kind of an interactive
> > +gitlink:git-filter-branch[1].
> > +
> > +
> > +OPTIONS
> > +-------
> > +--progress=<n>::
> > +	Insert 'progress' statements every <n> objects, to be shown by
> > +	gitlink:git-fast-import[1] during import.
> > +
> > +--signed-tags=(ignore|warn|strip|abort)::
> > +	Specify how to handle signed tags.  Since any transformation
> > +	after the export can change the tag names (which can also happen
> > +	when excluding revisions) the signatures will not match.
> > ++
> > +When asking to 'abort' (which is the default), this program will die
> > +when encountering a signed tag.  With 'strip', the tags will be made
> > +unsigned, with 'ignore', they will be silently ignored (i.e. not exported)
> > +and with 'warn', they will be exported, but you will see a warning.
> 
> I am not sure if abort should be the default.

I tried to be conservative.

> If a straight dump-restore is made without rewriting, the result will be 
> identical to the original, right?

Yep.

> The reason I mention a straight dump-restore is because ...
> 
> > +$ git fast-export master~5..master |
> > +	sed "s|refs/heads/master|refs/heads/other|" |
> > +	git fast-import
> 
> ... I find this a quite unrealistic example to assume that the data
> stream does not have some string and convert blindly without parsing.

That's what the warning after the example is about.  For quick and dirty 
operations, it is quite adequate.

Besides, I have the feeling that some people are more comfortable dumping 
the whole repository into a file, editing it, and fast-importing it.  That 
is what I referred to when I said "think of it as kind of an interactive 
filter-branch".

> On the other hand, we _could_ also have a separate filter that works on 
> input stream for fast-import, but that filter should know what the 
> fast-import input stream looks like (a simple sed does not cut it).

I agree that for most serious operations sed is not good enough.

> So unless the future direction is to deprecate filter-branch and replace 
> it with such a fast-import based filter in between fast-export and 
> fast-import, I think the use of fast-export is to make verbatim copy 
> without munging the contents, which leads me to think --signed-tag 
> option should default to "export it as-is".
> 
> ... which seem to be missing from the available values to the option.

You mean something like "--signed-tag=warn 2> /dev/null"?  How about a 
"--signed-tag=quiet" mode?

> > diff --git a/builtin-fast-export.c b/builtin-fast-export.c
> > new file mode 100755
> > index 0000000..48d0c54
> > --- /dev/null
> > +++ b/builtin-fast-export.c
> > ...
> > +/*
> > + * TODO:
> > + * - tags (--signed-tags=(ignore|warn|strip|abort)
> > + */
> 
> This comment is stale?

Correct.

Ciao,
Dscho