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Smart merge

Use the UnityYAMLMerge tool to merge scene and prefab files in a semantically correct way.
Read time 6 minutesLast updated 10 days ago
Use the UnityYAMLMerge tool to merge scene and prefab files in a semantically correct way. The tool can be accessed from the command line and is also available to third-party version control software.

Setting up smart merging in Unity

In the Version Control project settings (menu: Edit >
Project Settings

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>
Version Control

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), when you select a third-party version control tool in the Mode field, for example Perforce or Unity Version Control (UVCS), the Smart Merge is displayed. The menu has the following options:
  • Off: use only the default merge tool set in the preferences with no smart merging.
  • Premerge: enable smart merging, accept clean merges. Unclean merges will create premerged versions of base, theirs and mine versions of the file. Then, use these with the default merge tool.
  • Ask: enable smart merging but when a conflict occurs, show a dialog to let the user resolve it (this is the default setting).

Setting up UnityYAMLMerge for use with third-party tools

The UnityYAMLMerge tool is included with the Unity Editor. Assuming Unity is installed in the standard location, the path to UnityYAMLMerge is as follows:
On Windows:
C:\Program Files\Unity\Editor\Data\Tools\UnityYAMLMerge.exe
Or
C:\Program Files (x86)\Unity\Editor\Data\Tools\UnityYAMLMerge.exe
On macOS:
/Applications/Unity/Unity.app/Contents/Helpers/UnityYAMLMerge
To access this folder from the Finder, right-click the 
Unity.app
and select the 
Show Package Contents
option.
UnityYAMLMerge is shipped with a default fallback file (called mergespecfile.txt, also in the Tools folder) that specifies how it should proceed with unresolved conflicts or unknown files. This also allows you to use it as the main merge tool for version control systems (such as git) that don't automatically select merge tools based on file extensions. The most common tools are already listed by default in mergespecfile.txt but you can edit this file to add new tools or change options.
You can run UnityYAMLMerge as a standalone tool from the command line (you can see full usage instructions by running it without any arguments). Setup instructions for common version control systems are as follows:

P4V

  1. Go to Preferences > Merge.
  2. Select Other application.
  3. Click the Add button.
  4. In the extension field, type 
    .unity
    .
  5. In the Application field, type the path to the UnityYAMLMerge tool (see above).
  6. In the Arguments field, type 
    merge -p %b %1 %2 %r
  7. Click Save.
Then, follow the same procedure to add the 
.prefab
extension.

Git

Add the following text to your 
.git
or 
.gitconfig
file:
	[merge]	tool = unityyamlmerge	[mergetool "unityyamlmerge"]	trustExitCode = false	cmd = '<path to UnityYAMLMerge>' merge -p "$BASE" "$REMOTE" "$LOCAL" "$MERGED"

Mercurial

Add the following text to your 
.hgrc
file:
	[merge-patterns]	**.unity = unityyamlmerge	**.prefab = unityyamlmerge	[merge-tools]	unityyamlmerge.executable = <path to UnityYAMLMerge>	unityyamlmerge.args = merge -p --force $base $other $local $output	unityyamlmerge.checkprompt = True	unityyamlmerge.premerge = False	unityyamlmerge.binary = False

SVN

Add the following to your 
~/.subversion/config
file:
	[helpers]	merge-tool-cmd = <path to UnityYAMLMerge>

TortoiseGit

  1. Go to Preferences > Diff Viewer > Merge Tool and click the Advanced button.
  2. In the popup, type 
    .unity
    in the extension field.
  3. In the External Program field type:
	<path to UnityYAMLMerge> merge -p %base %theirs %mine %merged
Then, follow the same procedure to add the 
.prefab
extension.

Unity Version Control (UVCS)

  1. Go to Preferences > Merge Tools and click the Add button.
  2. Select External merge tool.
  3. Select Use with files that match the following pattern.
  4. Add the 
    .unity
    extension.
  5. Enter the command:
	<path to UnityYAMLMerge> merge -p "@basefile" "@sourcefile"  "@destinationfile" "@output"
Then, follow the same procedure to add the 
.prefab
extension.

SourceTree

  1. Go to Tools > Options > Diff.
  2. Select Custom in the Merge Tool dropdown.
  3. Type the path to UnityYAMLMerge in the Merge Command field.
  4. Type 
    merge -p $BASE $REMOTE $LOCAL $MERGED
    in the Arguments field.

Configuring mergerules.txt

To customize how UnityYAMLMerge merges files, configure the mergerules.txt file. This is available in the 
Editor/Data/Tools
folder of your Unity installation. The various configuration options are as follows.

Arrays

The arrays configuration section tells UnityYAMLMerge to treat the specified path as an array; either as a "set" with a key value, or as a "plain" array without key values. The default for all arrays is to do a hybrid mode and try to match with some known heuristics.
  • <mode> is one of "set" or "plain"

Example (as per default mergerules file)

[arrays]set *.GameObject.m_Component *.fileIDset *.Prefab.m_Modification.m_Modifications target.fileID target.guid propertyPathplain *.MeshRenderer.m_Materialsplain *.Renderer.m_Materials

Exclusions

The exclusions configuration section indicates which paths to exclude from merging. If both sides have been modified, they are then treated as a conflict and will show up for user input.
  • <mode> is one of "include", "exclude", "includeIfContains", "excludeIfContains"

Example (as per default mergerules file)

[exclusions]exclude *.MeshRenderer.m_Materials.*exclude *.SpriteRenderer.m_Materialsexclude *.SpriteRenderer.m_Colorinclude *.ParticleSystem.InitialModuleexclude *.ParticleSystem.*exclude *.ParticleSystem.InitialModule.*#excludeDepend *.MonoBehaviour m_Script ^m_excludeIfContains *.MonoBehaviour.* x y zexcludeIfContains *.MonoBehaviour.* r g b

Arguments

The 
--nomappinginoneline
argument is deprecated and no longer has any effect. Unity now always serializes inline mappings on one line, and the merge tool follows this behavior. This argument is ignored if provided.

Comparisons

The comparisons section takes into account negligible differences between float values to ignore per user settings. When enabled, floating point comparison is done relatively to account for relative error. You can configure comparison in the following ways:
  • "float" <float value to compare> (This sets epsilon to a default value close to machine epsilon)
  • "float" <float value to compare> <relative comparison value and absolute cutoff>
  • "float" <float value to compare> <relative comparison value> <absolute comparison cutoff>
The relative comparison value determines epsilon and how comparison will scale with the size of the floats’ relative error. The absolute comparison cutoff determines at which point float comparison switches from absolute to relative from zero (on a graph).
Note
Comparison values should be between float epsilon (~0.00000011921) and 1.0

Example

[comparisons]float *.Transform.m_LocalPosition.x 0.0000005float *.Transform.m_LocalPosition.y 0.0000005float *.Transform.m_LocalPosition.z 0.0000005float *.Transform.m_LocalRotation.x 0.00005 0.001float *.Transform.m_LocalRotation.yfloat *.Transform.m_LocalRotation.z 0.00005 0.001float *.Transform.m_LocalRotation.w

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