Running git-archive recursively over submodules

> I'm posting this for posterity.  It came out of an IRC discussion last
> night.  Google "git archive submodules" currently finds two scripts
> for the same task:
> 
> * http://kerneltrap.org/mailarchive/git/2008/3/29/1294614
>   Can pack arbitrary revisions, but seems to be highly specific to the
>   poster's setup.
> 
> * http://wiki.github.com/meitar/git-archive-all.sh/
>   Appears to work with normal repos (I haven't really tested) but only
>   packs HEAD.
> 
> Both have in common that they run git-archive in each submodule, and
> then merge the resulting tars.
> 
> The script below follows a different approach, based on the idea that
> all the objects are already there, you just need to help git find
> them.  This of course assumes that you have the submodules checked out
> (or at least cloned).  It builds an index that contains a flattened
> version of the repository and all submodules.  This works for any
> revision you specify.  The downside is that this does not respect
> .gitattributes.
> 
> The same trick can be used for other commands, so if people find this
> useful it could be added to git-submodule.
> 
> Warning: Error detection and such are left as an exercise to the user.
> 
> -- 8< --
> #!/bin/sh
> 
> export revision="$1"
> 
> export GIT_INDEX_FILE=".git/tmpindex"
> rm -f "$GIT_INDEX_FILE"
> 
> git read-tree $revision
> 
> export up="$(pwd)"
> 
> read_one_level () {
> 	export GIT_ALTERNATE_OBJECT_DIRECTORIES="$GIT_ALTERNATE_OBJECT_DIRECTORIES":$(
> 	    git submodule foreach 'echo "$up/$path/.git/objects"' |
> 	    grep -E -v '^(Entering|No submodule mapping found)' |
> 	    tr '\n' : |
> 	    sed 's/:$//'
> 	)
> 
> 	git submodule foreach '
> 		cd "$up"
> 		subcommit=$(git rev-parse :"$path")
> 		git rm --cached "$path"
> 		git read-tree -i --prefix="$path/" $subcommit
> 	' >/dev/null
> }
> 
> while git ls-files -s | grep -q ^160000; do
>     read_one_level
> done

> git archive --format=tar $(git write-tree)
> 
> rm -f "$GIT_INDEX_FILE"
> -- >8 --
> 

> Thomas Rast venit, vidit, dixit 15.02.2010 21:56:
> > while git ls-files -s | grep -q ^160000; do
> >     read_one_level
> > done
> 
> Am I blind, not seeing a recursion, or is there simply none? I reckon
> you're reading the super project and one level of submodules into the
> temporary index - which is fine for most purposes, of course. I would
> say this is iterating over the submodules of the super project.

> On Tuesday 16 February 2010 08:38:08 Michael J Gruber wrote:
>> Thomas Rast venit, vidit, dixit 15.02.2010 21:56:
>>> while git ls-files -s | grep -q ^160000; do
>>>     read_one_level
>>> done
>>
>> Am I blind, not seeing a recursion, or is there simply none? I reckon
>> you're reading the super project and one level of submodules into the
>> temporary index - which is fine for most purposes, of course. I would
>> say this is iterating over the submodules of the super project.
> 
> Well, the while condition reads "while there are submodule entries in
> my index".  The read_one_level function then replaces those submodules
> with their corresponding trees, which of course may again contain
> submodule entries.
>