What is Git?

Git is a distributed version control system (VCS) originally developed by Linus Torvalds for managing Linux source code without requiring a central server. It is also the primary VCS used by the Gnome and Free Desktop projects. You can get the latest version for your system and read a rich variety of online documentation at Git's Home. In particular, Pro Git by Scott Chacon is available in several languages for free online reading at Git Book, where you can also download the English version as a PDF, ebook, or mobi.

If you know nothing about version control, that doesn't matter. Just read Getting Started - About Version Control. There in the left column you can select your language.

Another good place to start is Good Resources for Learning Git and GitHub - not only if you want to use GitHub for #Pull Requests.

 git help

will give you a list of usual commands and

git help <command>

will show you the manual page of that command.

There are several GUIs available for git, e.g.:

git gui
gitk (shows the history)
SourceTree for Windows or Mac

and most IDEs have plugins for it.

What has that to do with Gnucash?

We have converted from Subversion to Git in order to take advantage of its branching and merging facilities, which are much richer than those provided by Subversion.

Our public repositories are mirrored on Github: for code, documentation and for the website. These are updated from the primary repository by commit hooks, so barring technical problems changes appear in these repositories within a few seconds of being committed to the primary.

svn.gnucash.org is just another name for code.gnucash.org, the server that hosts the canonical git repository, wiki, Mailing Lists, automated win32 builds, and the nightly builds of the documentation and API docs (via Doxygen) for both branchs. The old SVN repository is there too and it is possible to check out from it but since it doesn't take commits there's no reason to do so.

Using the Github Repository

Branches

There are are 2 important branches in most of our repositories:

master: is the default branch in git. New features and their documentation should be based on this branch. In the old svn days this was trunk. For convenience for users migrating from svn a trunk branch has been set up as an alias for the master branch but you are encouraged to switch to master as your main branch.
maint: Bugfixes, translations, improvements of the documentation should usually be applied on this branch.

Non-Committers should always work in a branch specific to the bug or feature being worked on, not the master or maint branch. Name the feature or working branch after the bug or feature - e.g. bug-12345 or invoice-new-button.

Non-Committers

There are 2 main ways to submit bug fixes, modifications or enhancements for review:

GitHub pull requests: These are preferred by the developers due to rich GitHub code review functionality.

Proceed to #Pull Requests.

Patches: A patch is essentially a specially formatted file containing a list of the files that have been changed, and for each file, before and after listings of the changed lines.

Patches

Patches - Set-Up

Create the directory you wish to hold your repository or repositories in and make it current. Assuming you wish it to be called github in your home directory:

 mkdir ~/github
 cd ~/github

Create a copy of the required repository on your PC by cloning:

 git clone https://github.com/Gnucash/gnucash.git

other URLs: https://github.com/Gnucash/gnucash-docs.git (documentation); https://github.com/Gnucash/gnucash-htdocs.git (website); See https://github.com/Gnucash for further repos e.g. with OS/distro specific build scripts.

The clone example above will create the local repository

 ~/github/gnucash

and also defines a remote named origin pointing to the cloned from repository which you can use in future as a shortcut instead of the full URL.

Change into the repository directory:

 cd gnucash

Only the default branch master will have been cloned. If you wish to work on a modification to the maint branch, create local branch maint to track your remote branch:

 git branch --track maint origin/maint

Patches - Create a working-branch

Open a bug in Bugzilla to attach your patch to if one doesn't already exist.
Use a particular working branch for only one bug or feature. This will make it much easier to make changes and generate new patches should that prove necessary.
Create a local (on your PC) branch to work in:

Bug fixes should branch from maint unless the bug applies only to the unstable version.

New features must branch from master.

The following example is for a new feature; substitute maint for master if you're doing a bug-fix.

Checkout the required branch to create the working-branch from (master or maint), e.g.:

 git checkout master

Note: checkout prepares your local repository ready for work on a particular branch by resetting all files back to how they were at the time they were last committed. It is much easier if you only checkout a branch after committing all changes you have made to the current branch. You will get a warning if you try to change branches and there are uncommitted changes. It is not wise to leave a file open in an editor while checking out a branch as you may accidentally save a version from another branch.

 git branch working-branch        # Creates branch working-branch from the current branch
 git checkout working-branch	   # make working-branch current

You are now ready to make and test your changes in your local working branch.

Patches - Commit

See http://wiki.gnucash.org/wiki/Documentation_Update_Instructions#Step_11_Commit_your_Changes

Patches - Sync your local master/maint from origin

After you have completed your changes, to minimize the chances of your future patch conflicting with any changes that may have been committed to the official GnuCash repositories while you were working:

Update the local master or maint branch (depending on which your working branch was created from) in your local repository from origin:

 git pull origin master

Rebase your working branch commits based on the updated master or maint:

 git rebase master working-branch

You can update both master and maint if you wish but you only need to update the branch on which your working branch was based.

Test again to make sure everthing works with the rebased code

Patches - Create Patch(es)

A patch file is created for each commit.

Use git rebase -i as necessary to make a clean series of patches for complex changes.
Use git format-patch to create the actual patches from your commits:

 cd ~/github/gncucash
 git format-patch origin/master..master

(or git diff) to prepare them.

Attach the resulting patch(es) to the bug report. It is not necessary to email anyone as the relevant people are automatically emailed when you attach a patch to a bug.
If a committer asks you to make changes, revise your original commit and make a new patch. Don't submit a patch to be applied on top of an old one. git-rebase -i can be very helpful if you have a series of patches.
Once the patch has been either merged or rejected, you can delete the local working branch:

 git checkout master
 git branch -D working-branch
 E.g.
 git branch -D bug-99999	# delete local branch bug-99999

Pull Requests

If you prefer, you can use a GitHub Pull Request instead of attaching a patch to a bug. You'll need to create a GitHub account if you haven't got one already and set it up for ssh access.

Suggested remote repository names for Non-Committers Using Pull Requests

Use the following names in your local PC repository for remote repositories:

upstream: The official repository to which only authorized developers can write. E.g.

github.com/Gnucash/gnucash

or

github.com/Gnucash/gnucash-docs

These are actually public mirrors for the real GnuCash official repositories.

origin: This is your personal writable GitHub repository. E.g.

github.com/[YOUR-GITHUB-USERNAME]/gnucash

or

github.com/[YOUR-GITHUB-USERNAME]/gnucash-docs

Pull requests are made from here to the upstream repository.

Pull Requests - Set-Up Your Personal GitHub Repository

Use Github's fork feature to set up a your own personal read-write enabled clone on GitHub:

In a web browser, go to https://www.github.com, login and search for Gnucash. Click on the link for the required repository, E.g.

 Gnucash/gnucash or Gnucash/gnucash-docs

Click on the Fork button at top right. This will create

 www.github.com/[YOUR-GITHUB-USERNAME]/gnucash-docs

Pull Requests - Set-Up a Local Repository on your PC

As you will eventually push your modified local repository branch back to your personal GitHub repository, it is useful to create your local PC repository by cloning from your personal GitHub repository, rather than the official GnuCash repository. The remote name origin in your local repository, is automatically set up to point to where you clone from (I.e. your personal GitHub repository).

Create the directory you wish to hold your repository or repositories in and make it current. Assuming you wish it to be called github in your home directory:

 mkdir ~/github
 cd ~/github

Clone from your remote personal repository origin:

 git clone git@github.com:<YOUR-GITHUB-USERNAME>/gnucash.git</tt>

The clone example above will create the local repository

 ~/github/gnucash

and also defines a remote named origin pointing to the cloned from repository which you can use in future as a shortcut instead of the full URL.

Change into the repository directory:

 cd gnucash

Only the default branch master will have been cloned. If you wish to work on a modification which should be applied to the maint branch, create local branch maint to track your remote branch:

 git branch --track maint origin/maint

Pull Requests - Create a working-branch

Create a branch to work in:

Bug fixes should branch from maint unless the bug applies only to the unstable version.

New features must branch from master.

Open a bug in Bugzilla to enable your work to be tracked if one doesn't already exist.

The following example is for a new feature and therefore uses master; substitute maint for master if you're doing a bug-fix.

Use a particular working branch for only one bug or feature. This will make it much easier to make changes and generate new patches should that prove necessary.

 git checkout master
 git branch working-branch        # Create branch working-branch from the current branch
 git checkout working-branch

Note: checkout prepares your local repository for work on a particular branch by resetting all files back to how they were at the time that branch was last committed. It is much easier if you only checkout a branch after committing all changes you have made to the current branch. It is not wise to leave a file open in an editor while checking out a branch as you may accidentally save a version from another branch.

You are now ready to make and test your changes in your local working branch.

Pull Requests - Commit

See http://wiki.gnucash.org/wiki/Documentation_Update_Instructions#Step_11_Commit_your_Changes

Pull Requests - Sync your local master/maint from origin

After you have completed and tested your changes, to minimize the chances of your future pull request conflicting with any changes that may have been committed to the official GnuCash repositories while you were working:

Update the local master or maint branch (depending on which your working branch is based) in your local repository from origin:

 git pull origin master

Rebase your working branch commits based on the updated master or maint:

 git rebase master working-branch

Test again to make sure everything works with the rebased code.

You can update both master and maint if you wish but you only need to update the branch on which your working branch was based.

Pull Requests - Push Back to Personal Repository

If you followed these instructions and cloned to your local working-branch from your personal github repository, then the remote name origin already points to your personal remote github repository. Check your defined remotes by:

 git remote -v

The output of the above should include:

 origin	git@github.com:<YOUR-GITHUB-USERNAME>/gnucash-docs.git (fetch)
 origin	git@github.com:<YOUR-GITHUB-USERNAME>/gnucash-docs.git (push)

so you can push your working-branch to your remote personal github repository by:

 git push origin working-branch
 E.g.
 git push origin bug-99999

If your remote named origin does not point to your personal github repository but you have another remote which does, then substitute your remote name for origin in the above command.

If you don't have a remote name that points to your personal github repository, then add a remote name that does, E.g. to add remote named mygithub:

 git remote add mygithub ssh://git@github.com/<YOUR-GITHUB-USERNAME>/gnucash

then git push mygithub working-branch

Pull Requests - Create Pull Request

Now log in to your GitHub account, go to your forked gnucash repository, select working-branch from the branch pick list, and click pull request. It's above the "last commit" line on the right in the directory view.
In the resulting form, give your pull request a title and describe its motivation. If it's associated with a bug, use the bug number and title for your title and paste the bug URL into the description. Note that GitHub descriptions use Markdown and that there's a preview tab to help you make sure that everything looks the way you want it.
Click the Send Pull Request button to the right of the description block.
If a developer requires changes to your pull request, amend your commits as necessary and force-push your branch. Don't make any changes to that working branch that aren't associated with the pull request!
Once the pull request has been either merged or rejected, you can delete the branch.

To delete the local branch:

 git branch -D working-branch
 E.g.
 git branch -D bug-99999	# delete local branch bug-99999

To delete the working branch from your personal remote github repository:

 git push <remote-name> :working-branch  # note space before :working-branch
 E.g.
 git push origin :bug-99999

Committers

Since 2014-02 all GnuCash repositories are pure git repositories:

gnucash
gnucash-on-windows: windows installer and build script moved here from gnucash/packaging
gnucash-docs
gnucash-htdocs (see #Conversion Notice)

Write Access

FAQ: Is it possible to get write access?

A: In principle yes, but we are quite conservative with giving out new SSH write accounts. For occasional changes people are encouraged to submit patches. We do add people as developers if they stick around, supply lots of patches, become highly involved in the project, hang out on IRC, and generally show some level of clue and prove some level of trust. But in the meantime, patches in Bugzilla and pull requests on github are the suggested route, as has been stated at other places. --Cstim 08:00, 8 January 2006 (EST)

Set up

Note: this set up presumes you already have commit access to the GnuCash repositories on code.gnucash.org. If you don't but believe you should, ask for this on the gnucash-devel mailing list.

Generate your ssh key pair

You'll need to generate a key-pair and provide the public half to the GnuCash repository administrator. To generate a key pair use

 ssh-keygen -t rsa -b 1024 -f gnucash-key

You can use any name you like instead of "gnucash-key".

You will also be prompted for a passphrase, with the option to leave it blank. If you provide a passphrase, you will be prompted to provide it every time you use your key. If you don't, anyone who gains access to your key can connect to whatever servers you protect with it.

Once you have the key configured correctly and have provided it to the GnuCash repository administrator, try

 ssh -i gnucash-key git@code.gnucash.org

You'll get the usual ssh question about the fingerprint for a new host. It should be 20:23:3d:df:f3:13:34:c1:32:ca:11:77:24:21:98:01. If it is, answer "yes" to add it to your known hosts file. If you get a message followed by a list of repositories, your setup is correct and you can proceed.

Next, you'll want to to configure your local ssh client to always provide this key when connecting to code.gnucash.org. In addition, ssh should always connect as user 'git'.

On linux, you can set this up by adding the following lines in your ssh config file (~/.ssh/config):

Host code.gnucash.org
IdentityFile ~/.ssh/gnucash-key
User git

(Continue with #Clone the Repositories)

Key generation under Windows

With MSYS

To set up ssh with the MSYS client, proceed exactly as above.

With Putty for TortoiseGit

For [TortoiseGit], you'll also need PuttyGen and Putty from [PuTTY]. Setting up Pageant to work with TortoiseGit is a bit involved, so we'll go through it step-by-step:

1. Use PuttyGen to convert your private key into Putty format. Launch puttygen, click the "load" button and select your private key file, then click the "save private key" button to save it in putty format.

2. Set up a Putty profile: Start Putty.

Set the Host URL to code.gnucash.org, port 22 on the Session page
Open Connection:SSH:Auth and at the bottom of the panel, for "Private key file for authentication" browse for the converted keyfile you made in the previous step.
Open Connection:Data and enter 'git' in the "Autologin username" text entry.
Return to the Session panel, enter a name (if you use code.gnucash.org configuring TortoiseGit will be less confusing) in the text entry named "Saved Sessions" and click the "save" button.
Click "open". If everything is done correctly, a command window will open and you'll see that message about terminal sessions not being allowed. If you are instead prompted for a password, you have messed up the username or key somehow and will need to contact the server admin to get your IP address unblocked.

(Continue with #TortoiseGit on Windows)

Clone the Repositories

Now clone the Github repository the same way as #Non-Committers. Since changes should not be pushed to the github repository, a good way to make sure that this doesn't happen by mistake is to use the same read-only URI given above for non-committers. Alternatively, fork the Gnucash repository to your Github account and clone that (use the read-write URI in that case).

Next add the repository on code.gnucash.org as a second remote, for example as 'upstream'.

 git remote add upstream git@code.gnucash.org:gnucash

Perhaps a better approach is to replace the push url:

git remote set-url --push origin git@code.gnucash.org:gnucash

That avoids confusion where to push and where to fetch.

That's it.

(Continue with #Committing)

TortoiseGit on Windows

Right-click a folder in Windows™ Explorer and select TortoiseGit:Settings. At the bottom of the Network panel of the resulting dialog box, click the "Browse" button for SSH Client and navigate to C:\Program Files\TortoiseGit\bin\TortoisePlink.exe, click "open" in the file chooser, the "OK" to dismiss the Settings box.
Right-click on a folder into which you want to check out (or already have checked out) Gnucash. If it's a fresh checkout, select TortoiseGit Checkout; otherwise select TortoiseGit:Relocate. Enter the URL as ssh://the-putty-session-name/gnucash. (Remember earlier where we said it would be less confusing if you use code.gnucash.org for the session name? That's because if you did the URL will be ssh://code.gnucash.org/repo/gnucash.)

You should now be able to commit changes via TortoiseGit.

Committing

Committing is simple:

 git add
 git commit

These two commands are used to record your changes locally.

 git push upstream local-branch:remote-branch

Will push your changes back to the master repository.

Branching and Merging

The "canonical" repositories at code.gnucash.org and their mirror at github.com/Gnucash have 2 active branches:

master is the development branch. All new features should be committed to this branch and this branch only. Unstable releases during the beta period leading up to a new stable release series will be tagged on this branch and the tarballs generated from the tag commits. Bugs reported against an unstable release should be checked to see if they exist on the stable release; if they do they should be reassigned to the stable release and fixed on maint, then merged. N.B.If for some reason a change is committed to master that should have been done in maint, cherry-pick that commit to maint. Merging master->maint would add all of the development changes into maint, which would be bad.

maint is the current stable release branch. All bugs reported on the released version should have the fixes committed to this branch and then merged to master. Stable releases will be tagged on this branch and the tarballs generated from the tag commits.

There are also archival branches, one for each stable release series no longer under development. Note that before 2.6 we used Subversion or CVS for version control and the practices were different, so you'll see different commit patterns when looking at historical branches.

The gnucash repository contains an archive branch which tracks master up to the point that the last subversion feature branch (webkit, if you're curious) was merged, except that new merge commits have been added to link the feature branch merges. It shows the merge points in the right order, but the merge commit dates are all from early 2014. It is of historical interest only.

There are several abandoned feature branches which were never integrated into GnuCash. They are also present for historical interest only.

Bugs and New Features

To repeat the policy in the description of the active branches:

Bug fixes should always be rebased onto the maint branch then merged to master unless either they don't affect maint or they are not going to be fixed on maint because the required changes are complex enough that it would risk making maint unstable.
New Features are always rebased or merged onto master. New features are not allowed on maint.

When and how to use branches depends on the complexity of the changes:

Small changes, which can be completed quickly and in a single commit, do not require a feature branch.
Larger changes, which might
- require more than one commit or
- take more than a few hours to write and test

should be done on a private branch which is rebased onto the appropriate main branch before pushing the changes to the main repository. This helps keep the main branch's history linear, which in turn makes it easier to read and displays better in a graphical tool.

Major changes,
- which are completed in stages which are made public in parts or
- which for any reason are best visualized as standing apart from the main branch,

should be merged with --no-ff to prevent them from fast-forwarding the main branch.

Bug Fix Feature Branch Example

 git checkout -b my-bug-fix maint
 # make changes, commit, test, fix, etc.
 git checkout maint
 git pull --rebase
 git rebase maint my-bug-fix
 # make && make check to ensure that you're not pushing a broken build!
 git push upstream maint
 git checkout master
 git pull --rebase
 git merge maint
 # rebuild and make check again
 git push upstream master

Major Feature Branch Example

 git checkout -b my-new-feature master
 # write and test the first phase of your feature, committing often.
 git checkout master
 git pull --rebase
 git merge --no-ff my-new-feature
 # rebuild and make check for safety
 git push upstream master
 git checkout my-new-feature
 # write the next phase and repeat until done.

Caution: When switching the branch you should cleanup your build dir to avoid "strange behavior". At least you should run make distclean before, but better might be

cd <yourbuild dir>
rm  -rf * && ../configure <your params> && make && make check

after switching. In case you are building intree you can run

git clean -fdx -e /.project -e /.cproject -e /.autotools -e /.settings/

instead to remove everything not in the repository with a few exceptions (-e ...). Above exceptions are files, where Eclipse stores its settings.

Resolving Merge Conflicts

Sometimes, e.g. after a new release, the first merge in gnucash-docs will result in an conflict about the version number: git status

On branch master You have unmerged paths. (fix conflicts and run "git commit") Changes to be committed: Unmerged paths: (use "git add <file>..." to mark resolution) both modified: configure.ac

configure.ac will now contain a section

<<<<<<< HEAD AC_INIT(gnucash-docs, 2.6.99)

=

AC_INIT(gnucash-docs, 2.6.4) >>>>>>> maint

Just remove the markers and the wrong section with your preferred editor.

Don't forget to run git commit -a to tell git, you are ready!

Link Bugzilla Entries

[FIXME:] While this worked with SVN/trac it seems not to work with github.

Often commits are related to Bugzilla entries. In this case the commit message should contain

Bug #<bug number>:<bug title> or
Bug #<bug number> - <bug title>.

You can specify it as the first line if the commit fully fixes the related bugzilla issue, or mention it in the body of the commit message otherwise.

Patches and Pull Requests

A common committer duty is handling patches and pull requests from non-committers. The procedure for both is:

Review the code for formatting, style, good coding practice, good commit message, etc. Make comments and get the submitter to make any necessary changes.
Download and apply the patch to the appropriate branch. If the change is complex you may want to make a local branch to work in.
Build and test. Discuss any problems with the submitter and get the patch in good shape, ready to commit.
If the patch is on the maint branch, do a test merge onto master. Resolve any merge issues with the submitter; if necessary, get a "patch to the patch" to resolve the merge conflicts.
Once everything is ready, merge your working branch into master or maint:
- Reset your local maint and/or master branches to remove any test merges.
- Pull them to get any commits others might have pushed while you're working.
- Apply the final patches or merge your working branch. When applying take care the patches are committed with the appropriate authorship.
  - If the patches were created with git format-patch and hence applied using git am this should be ok.
  - Also if the patches are in another repository or branch and you use git pull to apply them the author should be ok as well.
  - If the patches came as ordinary diff files to be applied with git apply, you should commit these changes with git commit --author "name <email>" with the proper author name and e-mail filled in.
- Merge maint into master if required; if there's a "patch to the patch" to handle conflicts between maint and master, use --strategy=theirs to the merge, then apply the repair patch and commit 'amending the merge commit:

 git checkout master
 git merge --strategy=theirs maint
 git apply patch-to-the-patch
 git commit -a --amend

Push the results
Close the pull request or mark the patches "Committed" in Bugzilla.

Pull Request Notes:

When processing a pull request it's safest to download the pull request as a (series of) patch(es). When you pull from the submitter's GitHub repository branch you risk conflicts because it hasn't been rebased to match the current state of the branch you're pulling to, though you can avoid that by making a working branch from the main branch commit that's at the base of the submitter's working branch. There may also be problems if the submitter has made changes to the working branch after making the pull request.
Note that code review comments can be made inline from the "Files Changed" tab of the pull request page on GitHub.

Other options exists as well; feel free to edit this wiki page.

Back to Development Process

Collaboration

With rare exceptions we don't want to clutter the master repository with feature branches, so how can two developers collaborate on one? There are several ways to go about it: You can pass patches between you over email, chat, or carrier pigeon; Git is designed to handle that easily (except for carrier pigeon transport, as that requires retyping the patch, which is a pain [Really?]). You can arrange for all of your repositories to be available on the net, and git pull amongst yourselves. Or you can use one of the public repositories like Github or Gitorious to manage your changes.

Git

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