Update GetBundle to use a custom subversion binary

GetBundle currently ships with it’s own svn binary from the 1.4 branch, but it is easy enough to make it use a different one.

1. Open TextMate
2. Go to TextMate > Preferences > Advanced
3. Click Shell Variables
4. Add a new variable called TM_SVN and set it to the path of the binary you want to use

Close the preference pane and open the bundle editor.

Bundles > Bundle Editor > Show Bundle Editor

Expand the GetBundle entry and in Install Bundle and Update Installed Bundles change:

SVN="${TM_BUNDLE_SUPPORT}/bin/svn"

to

SVN=${TM_SVN:-"${TM_BUNDLE_SUPPORT}/bin/svn"}