Branches

Developments to GBGP should be made from, and committed to, a ​branch rather than directly to the latest trunk version. This allows changes to be tested before merging the required changes back into the trunk. The trunk therefore represents a stable 'next potential release' state for GBGP. Branches can be temporary and might be for working on resolving a specific Trac Ticket.

Creating a branch

To create a branch of gbgp_src from the trunk use the ​svn copy ''SRC DST'' command:

svn copy https://svn.romsaf.org/gbgp/gbgp_src/trunk https://svn.romsaf.org/gbgp/gbgp_src/branches/<branch_name>

where <branch name> is a name of your choice which should reflect what you are working on. This prompts a text editor where you should describe the purpose of the new branch.

By default it is assumed that you wish to branch from the latest change version of the trunk. The -r flag can be used to specify the trunk revision from which a branch is required if this is not the latest. The -m flag could also be used when creating a branch to describe the contents of the branch.

svn copy [-r revision] SRC DST [-m "some text here"]

Similar branches may be created to store user versions of gbgp_doc or gbgp_test as required.

Checking out a branch

To make developments, the branch needs to be checked out to the local working SVN directory for editing as above, specifying the path name for the required branch, e.g.:

svn checkout https://svn.romsaf.org/gbgp/gbgp_src/branches/<branch_name> ${HOME}/<SVN_working_dir>/<branch_name>

Working in a branch

Code developments are then done within a branch as normal. To view the local changes made to a branch, use the ​svn status command.

Committing changes to a branch

When changes to a branch are ready to be updated in the repository, the code needs to be committed using the ​svn commit command.

svn commit -m "Some text here to describe the changes"

This will prompt a list of the changes to be committed.

When you are satisfied that all the changes you require to your branch have been committed and the GBGP Development Team are satisfied that it will be part of the next release, these changes will be merged back into the trunk by GBGP Admin.

Keeping up to date with changes to trunk

At some stage it may be necessary to update the trunk with latest developments while a user is still working in a particular branch. Users will be notified of any changes to trunk.

In order to keep a branch up to date with the latest version of the trunk while you are working on your branch, you may want to bring in the changes that have been made to the main trunk. This can be done using the ​svn merge command. You must first change directory to your branch's working copy: e.g.

cd ${HOME}/<SVN_working_dir>/<branch name>

For a branch was created or last updated at revision NNNN, the following command will merge all changes made in trunk since that revision into your branch.

svn merge -r NNNN:HEAD https://svn.romsaf.org/gbgp/gbgp_src/trunk

When you do this, you should see the list of updates that have been made to the trunk since you last brought in any changes (or since you branched). Note that this only results in changes to your working copy so you might want to commit them to the repository.

It is useful to preview the files which will be changed on performing a merge before going ahead using:

cd ${HOME}/<SVN_working_dir>/<branch name>
svn merge --dry-run -r NNNN:HEAD https://svn.romsaf.org/gbgp/gbgp_src/trunk

The merge command can be used separately on subdirectories and files within a branch as required.

If a conflict arises between the local copy of a file and the trunk copy to be merged, several versions of that file will be created (e.g. file.f90, file.f90.merge-left.rNNNN, file.f90.merge-right.rMMMM). In general, you will wish to replace the old version of a file (file.f90.merge-left.rNNNN) with the latest version from trunk (file.f90.merge-right.rMMMM). This can be done manually, and use the ​svn resolved command to indicate that the conflict has been addressed. This will tidy up the files created on merge.

Further information on branches are available in ​SVN reference: Branching and Merging

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