Subject: Re: Identify Commit ID from an Extracted Source Snapshot

From: Michael Schubert <[email-masked]>
Date: Fri, 17 Feb 2012 01:14:57 +0100

On 02/17/2012 12:53 AM, Jonathan Nieder wrote:
> Michael Schubert wrote:
> 
>> If your question is more like "how do I tell git to find out where
>> this old code fits in my history and eventually place it there",
>> the answer is: you cannot do it. No VCS will do this and especially
>> not Git.
> 
> Wouldn't it be possible to add the tags you want by walking through
> the commit log to find a matching commit for each tarball?

I read the question like "How do I insert / prepend my zipped
*pre-VCS* version (in)to my Git history in an automated fashion".

> For example:
> 
> 	# Usage: "GIT_DIR=<repository> tag-tars <tarballs>"
> 	# Arguments should be tarballs containing releases in
> 	# reverse-chronological order.
> 	# Should be run in an empty directory, which will be
> 	# used as a workspace.
> 
> 	# save stdin
> 	exec 3<&0
> 
> 	GIT_DIR=$(git rev-parse --resolve-git-dir "$GIT_DIR") || exit 1
> 	GIT_INDEX_FILE=$GIT_DIR/index.tag-tars
> 	export GIT_INDEX_FILE
> 
> 	if test -n "$(git ls-files -c -o | head -1)"
> 	then
> 		echo >&2 'fatal: I need an empty directory to work with'
> 		exit 1
> 	fi
> 
> 	for tar
> 	do
> 		# empty workspace
> 		git ls-files | xargs rm -f --
> 		rm -f "$GIT_INDEX_FILE"
> 
> 		# get tree name for tarball
> 		tar --strip-components=1 -xf "$tar"
> 		git ls-files -o | git update-index --add --stdin
> 		tree=$(git write-tree)
> 
> 		# tag the first commit found matching that tree, if any
> 		git rev-list master |
> 		while read cmit
> 		do
> 			if git diff-tree --quiet $cmit $tree
> 			then
> 				git tag -a ${tar%%.*} $cmit <&3
> 				break
> 			fi
> 		done
> 	done
> 
> Variation using --numstat and a path filter to find the closest commit
> ignoring some files instead of an exact match left as an exercise to
> the reader.

Nice, thanks!