[SR-Dev] How to import modules with full history

[Andrei Pelinescu-Onciul]

On Feb 19, 2009 at 03:21, Jan Janak <jan at iptel.org> wrote:
> Here is how you can import a kamailio module with full history (that means all
> previous commits done on the svn will also be visible in git) into the
> sip-router git repository.
> 
> First off, make sure you have a local copy of the sip-router git repository
> with kamailio history merged into it. You can find a step-by-step guide in the
> previous email with subject "Annotated git configuration file".

There's another way to do it: work in  a separate clone of the
kamailio repository
(git clone http://git.sip-router.org/kamailio kamailio_tmp.git), 
git-filter-branch it (like Jan described below) and
then when you're finished go to your sip-router repository (
(e.g. cd ~/sr.git; git checkout master) and "pull" it 
(git pull ~/kamailio_tmp.git sqlops_filtered) instead of the git-merge in
Jan's howto.

I prefer this way, because I don't like pulling all the repositories
(sip-router, ser and kamailio) into one. IMHO is better to have separate
copies, so it's hard to make mistakes like pushing the entire kamailio
in the public sip-router repository.
What's nice about git is that you can pull from any repository (you
don't need to fetch it into your tree).

> 
> I suppose that the module you want to import into the git repository will be
> based on the sources present in the kamailio svn trunk, so as the next step
> create a new branch based on the kamailio trunk:
> 
>   git co -b sqlops_filtered km/trunk
> 
> The name of the new branch is sqlops_filtered because I am importing kamailio
> sqlops module, "_filtered" because this branch will be used to filter commits.
> 
> Like revision numbers in svn (and unlike versions in cvs), git commits,
> identified by those cryptic sha1 hashes, record the state of _all_ files in
> the source tree at the time when the commit was made. But this is a problem
> because we only one to import the files in modules/sqlops directory and ignore
> all other files outside this directory. Even if you try to checkout an older
> commit which changed only files within modules/sqlops, you always get a full
> source tree, including files of all other modules. There is no way you can get
> a particular revision of selected files only--like you can do it with cvs.
> 
> But there is a solution: git-filter-branch. This is a handy git command which
> (among other things) can walk through all commits in the history of the
> current branch and tranform the commits into new commits with selected files
> only. To include only files in modules/sqlops we can do the following:
> 
>   git-filter-branch --subdirectory-filter modules/sqlops

WARNING: always verify the result after git-filter-branch. At least in
some git version (maybe even 1.5.*) it has problems when the history
doesn't begin at the beginning of the project (e.g. if modules/sqlops
was added at some later point and it's not in there form the start).

> 
> The command rewrite the history of the current branch, your current branch
> should be sqlops_filtered if you followed this guide from the beginning. If
> you investigate the history of the branch with git log, you should see only
> commits that are related to files in modules/sqlops. (The module contained
> only one commit at the time of writing of this memo so don't be surprised if
> you only see one commit in the history).
> 
> If you examine your current working directory now, you'll notice that the
> directory contains files from modules/sqlops in the top level directory. We
> need to put them back into modules/sqlopts before we can merge the branch into
> sip-router tree, this can be done with git-filter-branch again. But before we
> can run the command second time, we need to remove some residual files from
> the previous run:
> 
>   rm -rf .git/refs/original
> 
> And the following command will move all the files back to modules/sqlops 
> subdirectory:
> 
> git-filter-branch --index-filter 'git ls-files -s |
>    sed "s-\t-&modules/sqlopt/-" | 
>    GIT_INDEX_FILE=$GIT_INDEX_FILE.new git update-index --index-info && 
>    mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE' HEAD
> 
> The previous command might look a little scary, but it is documented in man
> git-filter-branch if you are interested in details.
> 
> If you examine your current working directory now, it should contain modules
> directory with sqlops subdirectory and all the module files there. This branch
> is now ready to be merged into the sip-router tree, so create a new branch,
> for example sqlops, based on the sip-router master branch:
> 
>   git co -b sqlops sr/master
> 
> And now you can merge branch sqlops_filtered into the newly created branch:
> 
>   git merge sqlops_filtered
> 
> And if everything went well, congratulations, you successfully imported your
> first kamailio module into the sip-router git repository. Branch
> sqlops_filtered is no more needed so you can safely delete it.
> 


Andrei