How can I teach `git-rerere` about the resolutions in an existing merge commit, with the least manual intervention

git-rerere is the exact solution to a problem I have ... except that the merges that need to be "learnt" have already been performed and are non-trivial to repeat.

How can I "teach" rerere about those commits with the minimum manual intervention.

Supposing that existing, but conflicting, branches A and B were merged together to form commit C with resolved conflicts. Then I was hoping to do:

• git checkout A
• git merge B
  • merge pauses when conflicts observed.
• git reset --soft C
  • working files are now in the desired final state - i.e. the conflicts were "resolved".
• git merge --continue
  • rerere sees the updated files as the appropriate resolution, and "learns" this resolution.

But the reset step doesn't work :(

• A --soft reset isn't permitted during a merge.
• A --mixed reset nukes MERGE_HEAD (and I assume generally screws around with the git state, such that the merge cannot be resumed)

EDIT:

Manually "resetting" the files, by checking out C before hand and copying over the relevant files works but is quite slow and tedious due to the large and complex nature of the repositor.

(lots of projects in separate folders, each with their own node_modules/packages folders that will tank the copy time, unless I target specific folders :( )

I'm hoping for something automated. #optimism

The contrib script rerere-train.sh is for this exact purpose