On Fri, Jan 01, 2016 at 10:54:00AM -0500, Stefan Monnier wrote:
> I have a program which tries to collect info from lots of branches and
> generate some table from that data into another branch.
>
> For performance reasons, I'd like to do that from fast-import, and as
> long as I know the name of all the files I need to consult, everything
> is fine since I can use the "ls" and "cat-blob" commands of fast-import
> to get efficiently the data I need.
>
> But I also need to look at some files whose names I don't know beforehand
> (i.e. all the files in some directories). If I do "cat-blob" on those
> directories I get some binary "thing" which I don't understand.
>
> So how do I get a directory listing from fast-inmport, i.e.
> like I can get with "git cat-file -p", but without having to fork
> a separate git process?
I'm not sure I understand your use case exactly, but is the directory
listing you want part of the newly-added objects from fast-import, or
does it already exist in the branches you are collecting from?
If the latter, I wonder if a separate "cat-file --batch" process could
give you what you need (it's a separate process, but you can start a
single process and make many queries of it; I assume your desire not to
add an extra process is to avoid the overhead).
But I think it won't pretty-print trees for you; it will give you the
raw tree data (which I imagine is what you are getting from cat-blob,
too). I'm not sure that's actually documented anywhere (it was part of
the original revisions of git, and hasn't changed since). But it is
basically:
tree = tree_entry*
tree_entry = mode SP path NUL sha1
mode = ascii mode, in octal (e.g., "100644")
path = <any byte except NUL>*
sha1 = <any byte>{20}
SP = ascii space (0x20)
NUL = 0-byte
So it is pretty simple to parse.
There may be a better way to do what you want with fast-import. I'm not
familiar enough with it to say.
-Peff
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