On Mon, Nov 03, 2008 at 07:33:21PM -0800, Andrew Arnott wrote:
> I have two projects, both with histories, that I want to merge into
> just one library. I'd like to preserve both histories, perhaps as if
> there were two branches being merged into one. (Although each project
> has its own branches that will make the history interesting).
>
> Is there a standard way to do this?
You have two options:
- just merge the history as if they were two branches:
# make a new combined repo
mkdir merged && cd merged && git init
# pull in each library
for lib in lib1 lib2; do
git fetch /path/to/$lib master:$lib
git checkout $lib
# do any pre-merging fixups
mkdir $lib
mv * $lib
git add -u
git add $lib
git commit -m "move files into $lib in preparation for project merge"
done
# and then merge; order isn't really important
git checkout lib1
git merge lib2
This method is nice because it preserves the original histories, and
you can still merge from the original projects (if people are still
working on them as individual projects).
Note that this is basically what the subtree merge strategy does, so
you could also use that. I showed all the steps here to give a sense
of what is going on, and because you might want to do additional
fixups besides moving files into the subtree.
- The other alternative is rewriting the history. The advantage here
is that the history looks as if the projects had always been part of
the repo, so there is no big rename event. You can even annotate the
commit messages to indicate which project is being worked on.
The downside, of course, is that having rewritten history, merges
with the original project become more difficult. But that is not a
problem if you are going to throw away the original repositories.
You can accomplish this with filter-branch:
mkdir merged && cd merged && git init
for lib in lib1 lib2; do
git fetch /path/to/$lib master:$lib
git checkout $lib
git filter-branch -f \
--index-filter '
git ls-files -s |
sed "s,\t,&'$lib'/," |
GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
git update-index --index-info &&
mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE' \
--msg-filter "sed '1s/^/[$lib] /'" \
$lib
done
and then merge the resulting branches as usual.
Hope that helps.
-Peff
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