Question

I have a repository for one of my projects that has a nested repository using the svn:externals property to update files from an external library. The problem is that I need to comment out one of the function declarations from one of the headers in this library, and carry around the modified header with the root repository.

Is there a way that this could be done, so that when the library is updated, it overrides that specific file with my version of it?

Answer 1

What you want sounds like a “vendor branch” scenario to me.

current repository

root
|-- myproject
    |
    -- mycode
    |
    -- library -> svn:externals to a remote svn or your own libraryproject

---

suggested repository

root
|-- myproject
    |
    -- mycode
    |
    -- library -> copied/branched from ^/vendor/library/current (modified at this location as much as you like)

|
-- vendor
   |
   --library
     |
     --current
     |
     --imported-version-1.0
     |
     --imported-version-1.1

---

How to create the layout

Create ^/vendor/library/current and DOWNLOAD the original unmodified library code into it.

svn commit ^/vendor/library/current
svn cp ^/vendor/library/current ^/vendor/library/imported-version-1.0 (tag the import)
svn cp ^/vendor/library/current ^/myproject/library (branch the code into your project)

modify ^/myproject/library and commit

---

How to update the library without losing your modifications

Download the latest original release of the library into ^/vendor/library/current OVERWRITING files.

svn commit ^/vendor/library/current (checks in the difference between the two library releases)
svn cp ^/vendor/library/current ^/vendor/library/imported-version-1.1 (tag the change)
cd /your-local-workspace/myproject/library (will be merge target)
svn merge ^/vendor/library/current (get all CHANGES from the upstream branch and apply them to your modified library)
svn commit

profit

---

Instead of branching “current” directly into your project you could branch to a “my-modified-libs” directory and make use of it via externals. This would be advised if you have multiple projects that need the same modified version of a library.

Keep in mind that vendor branches will have problems dealing with renames and deletes as those can not be tracked by overwriting. Cross-repository merging is a different and rather young topic for SVN.

If you try it out, give us feedback how it went 🙂

Christoph