SVNBackportExample < Main

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---+ Subversion -- Copying Changes Between Branches

Copying specific changes between branches is covered well in [[http://svnbook.red-bean.com/en/1.4/svn.branchmerge.copychanges.html#svn.branchmerge.copychanges.specific][Chapter 4 of Version Control With Subversion]], but I thought a real-life example might be helpful to some people.

I use version control for mantaining the PHP code for the Computational Lingustics database.  I made a small, cosmetic change to the table-generating code in a file called searchcorpus.php, in the trunk branch.  I wanted to backport it to release-2.2.  Here is the sequence I used.  Throughout this procedure my current directory was inside my working copy of release-2.2.

---++ Step 1: Locate the correct revision number.

<verbatim>
$ svn log svn://lemur.ling.washington.edu/admin/compling-database/trunk/searchcorpus.php
------------------------------------------------------------------------
r196 | brodbd | 2007-10-25 15:31:05 -0700 (Thu, 25 Oct 2007) | 1 line

searchcorpus.php: Improve look of tables by inserting &nbsp; instead of empty fields.
------------------------------------------------------------------------
r106 | brodbd | 2007-10-16 16:38:04 -0700 (Tue, 16 Oct 2007) | 1 line
...
</verbatim>

Now I know I want revision 196.

---++ Step 2: Merge in the change.

<verbatim>
$ svn merge -c 196 svn://lemur.ling.washington.edu/admin/compling-database/trunk/searchcorpus.php
U    searchcorpus.php
</verbatim>

This pulled in the changes to searchcorpus.php from revision 196 (and only revision 196) of trunk and applied them to my working copy.  I then ran =svn diff searchcorpus.php= to make sure the merge did what I wanted.  If not, I could have used =svn revert= to back out the changes.

---++ Step 3: Commit the change.

<verbatim>
$ svn commit -m "searchcorpus.php: Backport cosmetic fixes from trunk r196."
Sending        searchcorpus.php
Transmitting file data .
Committed revision 197.
</verbatim>

Notice that my commit message indicates I'm importing changes from a specific revision number of another branch.  This kind of bookkeeping is important in a complex project to make sure you don't accidentally merge the same change twice.

While this case is a simple one involving only one file, this same concept works for revisions that encompass multiple files or even whole directory trees, including file additions or deletions.  This gives =svn merge= a bit of an edge over =svn diff= followed by =patch= when porting complicated changes.

-- Main.DavidBrodbeck - 25 Oct 2007
Topic revision: r1 - 2007-10-25 - DavidBrodbeck