Git-NECI
Git and NECI
I've been discussing this for a while, and I'm keen to do a trial run to see if people are comfortable with using git. The move-over from svn to git is reasonably painless, but it isn't possible to easily use both svn and git from more than one repository. I'll therefore maintain the connection with the svn (through git-svn) until such time as we might transfer fully. The upshot of this is that the changes may take a day to filter through back and forth between git and svn versions. If you use just one or the other then changes will be immediate.
I'm going to host it on my home on scepter. Access will be via ssh. At the moment, I'd like people to test checking it out, and see how it would fit into their workflow. I've included some rudimentary instructions below, but there are some tutorials online (e.g. http://git.or.cz/course/svn.html ), and man gittutorial also provides some help. I would advise creating your own local sandbox repository to play and test things out on (separate from NECI).
To get it up and running successfully, it's sensible to have a public key setup (see below). After that, try the checkout commands below.
You may also find JSS's Git page useful. --alex 17:04, 1 October 2009 (BST)
Public Key Setup
You can see if you have one with
ls ~/.ssh/id_?sa.pub
If you don't, you can generate one with:
ssh-keygen -t dsa
I'm a security slacker, so I don't use a passphrase, but I'm sure JSS can let you know about exciting combinations of keyrings and passphrases if you want to use them.
You can copy the key to scepter (if you have an rsa, change dsa to rsa)
scp ~/.ssh/id_dsa.pub @scepter: ssh scepter cat ~/id_dsa.pub >>~/.ssh/authorized_keys rm ~/id_dsa.pub exit
Now test whether you can access scepter without a password
ssh scepter
Setting up git prompts
There's a nice little prompt utility which allows you to add git information to your prompt and provides tab-completion for the git subcommands, options, branch names etc.
wget "http://repo.or.cz/w/git.git?a=blob_plain;f=contrib/completion/git-completion.bash;hb=HEAD" -O ~/.gitprompt.bash
then in your .bashrc add to the end:
source ~/.gitprompt.bash PS1='\u@\h:\w$(__git_ps1 " [%s]")\$ '
Feel free to customize your prompt otherwise. Mine is
PS1="\[\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~} ${STY}\007\]\u@\h:\w$(__git_ps1 " [%s]")\$"
Cloning the NECI repository
Go to your favourite directory
cd ~/NECI git clone scepter:~ajwt3/NECI.git SOURCEgit
This will create a directory ~/NECI/SOURCEgit
You'll want to use the following commands for the moment
git status git add git commit git pull git push git help git help status (etc.)
Eventually there will be branching and merging (next week hopefully). Then we can have some real fun. DO NOT USE git svn on this repository. It will likely break things horribly owing to creating multiple different histories.
--alex 17:00, 1 October 2009 (BST)
For ease of use you can add some extra commands to your .git/config file:
[alias]
co = checkout
ci = commit
[branch "master"]
remote = origin
merge = master
The aliases reduce key-strain, and the branch section means you can type `git pull' without specifying a remote and branch.
Git on sword and tardis
git is not currently installed globally on sword and tardis, but I have installed a version local to me which all can use. Just add
export PATH=$PATH:~ajwt3/local/bin
to your .bashrc on those machines.
--alex 11:00, 6 October 2009 (BST)
Thoughts from an svn user
Just thought I'd give some tips to people who have been svn users about the main differences that I have come across, and some things to beware of.
Your repository is arranged as separate commits in separate branches. 'git branch' will show you the branch you are on, and the others in the repository. 'git checkout branchname' will allow you to swap branches, and 'git checkout -b newbranchname' will allow you to create a new branch. You can then modify the branches, make local commits to them, and merge them back in when you want (or not!). 'git status' will show you any changes to the files in the branch so you can decide whether to commit them or not. Note that checkout has a very different meaning to svn. To commit is also different. You have local commits, and commits to the main branch (you can only commit to this branch at the moment), which are done separately (they are one and the same in svn.) To make a local commit (which needs to be done before a main 'push' - gits name for pushing changes out to a non-local branch), you have to first add the code which makes up that commit. You do that with 'git add file.f90', and then to commit that to the branch as a commit, use 'git commit'. Alternatively, 'git commit -a' will add all modified files and commit in one go.
If you are in the middle of something, then want to work on something else, you can either create a new branch, or simply use 'git stash'. This will stash your changes out of sight and revert your code in that branch to the version at the last commit. You can then work on something else, and then reapply your changes you made at the stash point at a later date. To recover what you stashed and apply the changes to your current branch (it doesn't have to be the same one you stashed from), then you can use 'git stash apply'.
Once you have committed, you may want to merge your changes back into the master branch, since this is currently the only hosted branch on scepter. To do this, change branch to master, then do 'git merge branchtomerge' and the changes will be merged into master. These changes however are still only on your local copy, so you will want to use 'git push' to push them out to everyone who wants to update to get your changes. To update your code to the latest version of the master branch, you can use 'git pull' to get the changes up to date. 'git status' should then show no changes.
Finally, gitk (or qgit) will open up a nice gui, which will show all the log messages and commit history for the local repository you are on. To show the history for all the branches, you can use 'gitk --all'. The links are basically pointers to copies of the code which can be used to trance the development. As an aside, you should initially use git OR svn to make changes to neci, since changing at both will muck up the histories. Also, git and its branching facility, which is the main benefit, will only work if people make commits (local at least - they don't necessarily also need to be pushed) regularly and often. Remember, if you are only making a local commit, it won't break everyone elses code, so there is no reason not to make them!
Hopefully this is enough to get started, but feel free to add more things you find interesting/useful.
--ghb24 16:13, 5 October 2009 (BST)
Initial Setup
Some information on how this repository was setup initially
ajwt3@scepter:~> mkdir NECI.git ajwt3@scepter:~> cd NECI.git ajwt3@scepter:~/NECI.git> git init --bare --shared=group Initialized empty shared Git repository in /home/ajwt3/NECI.git/ ajwt3@scepter:~> cd .. ajwt3@scepter:~> chgrp -R alavi NECI.git/ ajwt3@scepter:~> chmod -R g+w NECI.git/
Then back to ajax
ajwt3@ajax:~/NE-CI/SOURCE [master]$ git remote add origin scepter:~ajwt3/NECI.git ajwt3@ajax:~/NE-CI/SOURCE [master]$ git push origin master ajwt3@ajax:~/NE-CI/SOURCEgit2 [master]$ cd .. ajwt3@ajax:~/NE-CI$ git clone scepter:~ajwt3/NECI.git SOURCEgit2 ajwt3@ajax:~/NE-CI$ cd SOURCEgit2/ ajwt3@ajax:~/NE-CI/SOURCEgit2 [master]$
Thanks to JSS for pointing out the bare and shared flags. --alex 17:19, 1 October 2009 (BST)