Handling Patches

Patches are a useful concept for handling local code modifications. They can be handy e.g. for transferring changes from one branch to another (or from one computer to another).

1) Producing a patch

A patch is a file which contains code modifications in "diff" format. You can easily write all local modifications in an svn working copy to a file by doing:

svn diff > patch.diff

This will produce a file called 'patch.diff' which contains all the changes. If you only want the changes from specific files or directories, you can do:

svn diff someDir/ someFile.f90 > patch.diff

If you want to produce a patch of a certain revision (let's say rev. 1234) in an svn repository, you can do:

svn diff -c1234 > patch.diff

This will include all changes made in that particular revision. If you want a patch of all modifications in a given range of revisions, do:

svn diff -r1234:5678 > patch.diff

This will include the modifications of all revisions after 1234 up to (and including) 5678. The changes of revision 1234 will not be included.

2) Applying a patch

Once you have a patch file, you can apply it e.g. to another svn branch (or even to a directory which is not under version control). This is done via:

patch -p0 < patch.diff

This will apply the changes from the patch file to the current directory.

3) Reverting a particular revision

A particular revision can be reverted by producing a diff of that revision and appling it reversely ("-R"):

svn diff -c1234 > patch.diff
patch -p0 -R < patch.diff