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You can either set default values by simple assignment, in which case all projects will inherit the values when SubVersion is selected for SCM Type. Another option can be to use if statement to check for SVNInstanceCode and setup different values based on the SVN instance selected by user. The second option provides a better approach if you have more than one repository and the structure of folders may be different among them. 
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Default Script Variables
Field Name | Type | Description |
|---|---|---|
SVNInstanceCode | String | The default SCM Instance Code for SCM SVN sources. |
TrunkScript | String | The default value/script for Trunk Script of SCM SVN sources. |
BranchScript | String | The default value/script for Branch Script of SCM SVN sources. |
TagScript | String | The default value/script for Tag Script of SCM SVN sources. |
CheckoutFolderScript | String | The default value/script for Checkout Folder of SCM SVN sources. |