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(The example code below is from the first time this was done)
NOTE: if your work on a branch requires changing files in a subtree, be sure to commit those changes separately. This will aid the future subtree split of those files back to the external.
First step is to create a branch that contains the changes you want to move back to the external (ACME-climate/cime in this case). The branchname should follow ACME conventions. NOTE: the command below must be issues from the top directory of ACME.
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