• if you don't have a local master branch tracking origin/master (git branch|grep master is empty)

git checkout --track -b master origin/master

• if you already have a local master branch tracking origin/master

git checkout master
# make sure the local "master" branch is up-to-date
git pull --ff origin master
# merge the branch into the local "master" branch
git merge --log --no-ff origin/branch_to_merge # for older git version, make sure merge.summary is true and skip --log
git log -1 # make sure you see a correct merge message (with summary), if not abort
gitk # optional, look if the commit tree looks ok
# only if everything is ok and you looked at the log
# push the changes on the local "master" branch to the repository "master" branch
git push origin master:master 

• if you did something wrong and pushed, and it cannot be easily corrected by a git revert, send an email to sr-dev@lists.sip-router.org asking to revert master to the previous state (this should be avoided in general since it would cause extra work for all people who fetched or pulled master in the meantime)

• if you need to abort or undo a merge attempt, you don't have any local changes that you want to keep and you haven't pushed back to origin (if you did, see above), use:

git reset --hard ORIG_HEAD  # WARNING: all local changes to the current branch will be lost

• don't try to merge the reverse way, e.g.: git checkout my_branch; git merge master; git push origin my_branch:master. The merge is equivalent to the above one (from the code point of view), but the merge commit message will be wrong.

If all you want to do is commit some changes you have in a local branch (called "my_local_branch" from now on), then you could use:

# change to my local branch
git checkout my_local_branch
# make sure we have the latest version of the "origin" branches
git fetch origin
# rebase "my_local_branch" to the current origin/master
git rebase origin/master
# if everything is ok and you don't have any rebase conflicts, push the 
# changes to the repository master branch
git push --ff origin my_local_branch:master