====== Keep Data in .git/refs ======
Git keeps references to heads (branches) and tags in .git/refs. This is very convenient because you can obtain the SHA1 ID of any tag just by doing cat .git/refs/tags/<tag_name>.

But this mechanism only works if you do not run git gc. The garbage collector packs tags by default, that means the files from .git/refs/tags will be removed and their SHA1 IDs will be stored in file .git/packed-refs instead.

To prevent this you can use the following in your .git/config:
<code>
[gc]
     packrefs = 0
</code>
See ''man git-pack-refs'' for more details.

====== Avoiding Tag Collisions ======
If you fetch tags from multiple remote repositories, it may happen that they will generate conflicts because all tags are stored in .git/refs/tags directory. This will happen, for example, if you fetch objects from both the sip-router git repository and also the repository at http://git.sip-router.org/ser. The reason is that both of them originate from a single cvs repository and thus they contain tags with identical names.  To avoid this situation you can do the following in your .git/config:

<code>
[remote "sr"]
    ....
    fetch = refs/tags/*:refs/tags/sr/*
    tagopt = --no-tags

[remote "cvs"]
    ....
    fetch = refs/tags/*:refs/tags/cvs/*
    tagopt = --no-tags
</code>

The configuration above will fetch all tags from both repositories explicitly and will store them in subdirectories under .git/refs/tags to avoid conflicts in file names. Because you download tags explicitly you can tell git-fetch not to download any tags using the tagopt option.

====== GIT commands for merging of modules  ======
This will show you how the git commands to merge modules, e.g. ser's avpops module is removed and K's avpops module is used as comon module.
<code>
# we start in the local master branch
git checkout master

# create a new local branch called "darilion/avpops" based on 
# the remote master branch, and checkout into the newly created branch
git checkout -b darilion/avpops origin/master

# remove the old ser module
git rm -r modules_s/avpops/

# move the Kamailio module into the common modules directory
git mv modules_k/avpops/ modules/

# do whatever is need, eg. modify the code, ...

# check if sip-router builds and the code is working as expected

# check the status (modified files)
git status

# add all modifications for the next commit
git add .

# commit the changes (which were added in the previous step)
# (this will commit into the local working branch, in this case darilion/avpops)
# make sure to add a commit message according to these rules:
#   http://sip-router.org/wiki/devel/git-commit-guidelines
git commit

# verify the commit
git log -1

# prepare for push into the remote master branch: make sure
# that our local branch is up2date with commits added to 
# remote main branch
git fetch origin
git rebase origin/master

# push our changes from the local "darilion/avpops" branch 
# into the remote master branch
git push origin darilion/avpops:master

# cleanup: change into another local branch and delete the local avpops branch
git checkout master
git pull --rebase origin master # fetch previously commited commit
git branch -d darilion/avpops
</code>