Preparing the Tree

If this is your first import after the switch to SVN, you will have to flatten and clean up the vendor tree, and bootstrap merge history in the main tree. If not, you can safely omit this step.

During the conversion from CVS to SVN, vendor branches were imported with the same layout as the main tree. For example, the foo vendor sources ended up in vendor/foo/dist/contrib/foo, but it is pointless and rather inconvenient. What we really want is to have the vendor source directly in vendor/foo/dist, like this:

% cd vendor/foo/dist/contrib/foo
% svn move $(svn list) ../..
% cd ../..
% svn remove contrib
% svn propdel -R svn:mergeinfo
% svn commit

Note that, the propdel bit is necessary because starting with 1.5, Subversion will automatically add svn:mergeinfo to any directory you copy or move. In this case, you will not need this information, since you are not going to merge anything from the tree you deleted.

Check the dist tree and perform any cleanup that is deemed to be necessary. You may want to disable keyword expansion, as it makes no sense on unmodified vendor code. In some cases, it can be even be harmful.

% svn propdel svn:keywords -R .
% svn commit

Bootstrapping of svn:mergeinfo on the target directory (in the main tree) to the revision that corresponds to the last change was made to the vendor tree prior to importing new sources is also needed:

% cd head/contrib/foo
% svn merge --record-only ^/vendor/foo/dist@12345678 .
% svn commit

With some shells, the ^ in the above command may need to be escaped with a backslash.

Importing New Sources

Prepare a full, clean tree of the vendor sources. With SVN, we can keep a full distribution in the vendor tree without bloating the main tree. Import everything but merge only what is needed.

Note that you will need to add any files that were added since the last vendor import, and remove any that were removed. To facilitate this, you should prepare sorted lists of the contents of the vendor tree and of the sources you are about to import:

% cd vendor/foo/dist
% svn list -R | grep -v '/$' | sort > ../old
% cd ../foo-9.9
% find . -type f | cut -c 3- | sort > ../new

With these two files, the following command will list removed files (files only in old):

% comm -23 ../old ../new

While the command below will list added files (files only in new):

% comm -13 ../old ../new

Let us put this together:

% cd vendor/foo/foo-9.9
% tar cf - . | tar xf - -C ../dist
% cd ../dist
% comm -23 ../old ../new | xargs svn remove
% comm -13 ../old ../new | xargs svn add

Check properties on any new files:

Once you have committed the new vendor release, you should tag it for future reference. The best and quickest way is to do it directly in the repository:

% svn copy ^/vendor/foo/dist svn_base/vendor/foo/9.9

To get the new tag, you can update your working copy of vendor/foo.

Merging to -HEAD

After you have prepared your import, it is time to merge. Option --accept=postpone tells SVN not to handle merge conflicts yet, because they will be taken care of manually:

% cd head/contrib/foo
% svn update
% svn merge --accept=postpone ^/vendor/foo/dist

Resolve any conflicts, and make sure that any files that were added or removed in the vendor tree have been properly added or removed in the main tree. It is always a good idea to check differences against the vendor branch:

% svn diff --no-diff-deleted --old=^/vendor/foo/dist --new=.

--no-diff-deleted tells SVN not to check files that are in the vendor tree but not in the main tree.

If any changes are required for the world to build with the new sources, make them now — and test until you are satisfied that everything build and runs correctly.

Commit

Now, you are ready to commit. Make sure you get everything in one go. Ideally, you would have done all steps in a clean tree, in which case you can just commit from the top of that tree. That is the best way to avoid surprises. If you do it properly, the tree will move atomically from a consistent state with the old code to a consistent state with the new code.