Subversion Merge: How to Cleanly Re-integrate a ‘Definitive’ Branch

svn

We have been experimenting with a new technique to manage our release branches.

Generally, we maintain our current release on the trunk, and create release branches for each release. The release branch is where active development usually occurs, and the trunk is used for bug fixes on the current release.

We have been periodically merging the bug fixes from the trunk into the release branch (weekly).

Now that we are ready for another release, we would like to merge the release branch into the trunk. Unfortunately, this leads to many conflicts (> 50). At first I was surprised, but now I understand that Subversion cannot easily rectify the changes in the branch with what exists in the trunk.

Is there a way to tell Subversion to use all of the versions of the files in the branch when integrating back into the trunk? We know that the branch versions of files are 'correct'.

As an alternative, we could theoretically abandon the trunk and just work off of the branch(es) – branching from the branch for releases.

We use TortoiseSVN and Subclipse.

Best Answer

From the output of svn help merge:

--accept ARG

specify automatic conflict resolution action ('postpone', 'base', 'mine-conflict', 'theirs-conflict', 'mine-full', 'theirs-full', 'edit', 'launch')

To accept the branch changes when merging to the trunk, you need the "--accept theirs-full" option.

I don't think TortoiseSVN 1.6.2 has an equivalent option in the GUI. You can still interactively resolve conflicts by selecting "use repository" as each conflict is encountered during the merge.

Related Solutions

What do “branch”, “tag” and “trunk” mean in Subversion repositories

Hmm, not sure I agree with Nick re tag being similar to a branch. A tag is just a marker

Trunk would be the main body of development, originating from the start of the project until the present.
Branch will be a copy of code derived from a certain point in the trunk that is used for applying major changes to the code while preserving the integrity of the code in the trunk. If the major changes work according to plan, they are usually merged back into the trunk.
Tag will be a point in time on the trunk or a branch that you wish to preserve. The two main reasons for preservation would be that either this is a major release of the software, whether alpha, beta, RC or RTM, or this is the most stable point of the software before major revisions on the trunk were applied.

In open source projects, major branches that are not accepted into the trunk by the project stakeholders can become the bases for forks -- e.g., totally separate projects that share a common origin with other source code.

The branch and tag subtrees are distinguished from the trunk in the following ways:

Subversion allows sysadmins to create hook scripts which are triggered for execution when certain events occur; for instance, committing a change to the repository. It is very common for a typical Subversion repository implementation to treat any path containing "/tag/" to be write-protected after creation; the net result is that tags, once created, are immutable (at least to "ordinary" users). This is done via the hook scripts, which enforce the immutability by preventing further changes if tag is a parent node of the changed object.

Subversion also has added features, since version 1.5, relating to "branch merge tracking" so that changes committed to a branch can be merged back into the trunk with support for incremental, "smart" merging.

How to ignore files in Subversion

(This answer has been updated to match SVN 1.8 and 1.9's behaviour)

You have 2 questions:

Marking files as ignored:

By "ignored file" I mean the file won't appear in lists even as "unversioned": your SVN client will pretend the file doesn't exist at all in the filesystem.

Ignored files are specified by a "file pattern". The syntax and format of file patterns is explained in SVN's online documentation: http://svnbook.red-bean.com/nightly/en/svn.advanced.props.special.ignore.html "File Patterns in Subversion".

Subversion, as of version 1.8 (June 2013) and later, supports 3 different ways of specifying file patterns. Here's a summary with examples:

1 - Runtime Configuration Area - `global-ignores` option:

This is a client-side only setting, so your global-ignores list won't be shared by other users, and it applies to all repos you checkout onto your computer.
This setting is defined in your Runtime Configuration Area file:
- Windows (file-based) - C:\Users\{you}\AppData\Roaming\Subversion\config
- Windows (registry-based) - Software\Tigris.org\Subversion\Config\Miscellany\global-ignores in both HKLM and HKCU.
- Linux/Unix - ~/.subversion/config

2 - The `svn:ignore` property, which is set on directories (not files):

This is stored within the repo, so other users will have the same ignore files. Similar to how .gitignore works.
svn:ignore is applied to directories and is non-recursive or inherited. Any file or immediate subdirectory of the parent directory that matches the File Pattern will be excluded.

While SVN 1.8 adds the concept of "inherited properties", the svn:ignore property itself is ignored in non-immediate descendant directories:

cd ~/myRepoRoot                             # Open an existing repo.
echo "foo" > "ignoreThis.txt"                # Create a file called "ignoreThis.txt".

svn status                                  # Check to see if the file is ignored or not.
> ?    ./ignoreThis.txt
> 1 unversioned file                        # ...it is NOT currently ignored.

svn propset svn:ignore "ignoreThis.txt" .   # Apply the svn:ignore property to the "myRepoRoot" directory.
svn status
> 0 unversioned files                       # ...but now the file is ignored!

cd subdirectory                             # now open a subdirectory.
echo "foo" > "ignoreThis.txt"                # create another file named "ignoreThis.txt".

svn status
> ?    ./subdirectory/ignoreThis.txt        # ...and is is NOT ignored!
> 1 unversioned file

(So the file ./subdirectory/ignoreThis is not ignored, even though "ignoreThis.txt" is applied on the . repo root).

Therefore, to apply an ignore list recursively you must use svn propset svn:ignore <filePattern> . --recursive.
- This will create a copy of the property on every subdirectory.
- If the <filePattern> value is different in a child directory then the child's value completely overrides the parents, so there is no "additive" effect.
- So if you change the <filePattern> on the root ., then you must change it with --recursive to overwrite it on the child and descendant directories.
I note that the command-line syntax is counter-intuitive.
- I started-off assuming that you would ignore a file in SVN by typing something like svn ignore pathToFileToIgnore.txt however this is not how SVN's ignore feature works.

3- The `svn:global-ignores` property. Requires SVN 1.8 (June 2013):

This is similar to svn:ignore, except it makes use of SVN 1.8's "inherited properties" feature.
Compare to svn:ignore, the file pattern is automatically applied in every descendant directory (not just immediate children).
- This means that is unnecessary to set svn:global-ignores with the --recursive flag, as inherited ignore file patterns are automatically applied as they're inherited.

Running the same set of commands as in the previous example, but using svn:global-ignores instead:

cd ~/myRepoRoot                                    # Open an existing repo
echo "foo" > "ignoreThis.txt"                       # Create a file called "ignoreThis.txt"
svn status                                         # Check to see if the file is ignored or not
> ?    ./ignoreThis.txt
> 1 unversioned file                               # ...it is NOT currently ignored

svn propset svn:global-ignores "ignoreThis.txt" .
svn status
> 0 unversioned files                              # ...but now the file is ignored!

cd subdirectory                                    # now open a subdirectory
echo "foo" > "ignoreThis.txt"                       # create another file named "ignoreThis.txt"
svn status
> 0 unversioned files                              # the file is ignored here too!

For TortoiseSVN users:

This whole arrangement was confusing for me, because TortoiseSVN's terminology (as used in their Windows Explorer menu system) was initially misleading to me - I was unsure what the significance of the Ignore menu's "Add recursively", "Add *" and "Add " options. I hope this post explains how the Ignore feature ties-in to the SVN Properties feature. That said, I suggest using the command-line to set ignored files so you get a feel for how it works instead of using the GUI, and only using the GUI to manipulate properties after you're comfortable with the command-line.

Listing files that are ignored:

The command svn status will hide ignored files (that is, files that match an RGA global-ignores pattern, or match an immediate parent directory's svn:ignore pattern or match any ancesor directory's svn:global-ignores pattern.

Use the --no-ignore option to see those files listed. Ignored files have a status of I, then pipe the output to grep to only show lines starting with "I".

The command is:

svn status --no-ignore | grep "^I"

For example:

svn status
> ? foo                             # An unversioned file
> M modifiedFile.txt                # A versioned file that has been modified

svn status --no-ignore
> ? foo                             # An unversioned file
> I ignoreThis.txt                  # A file matching an svn:ignore pattern
> M modifiedFile.txt                # A versioned file that has been modified

svn status --no-ignore | grep "^I"
> I ignoreThis.txt                  # A file matching an svn:ignore pattern

ta-da!