Can I tell Git to re-use the conflict resolution from an existing merge commit? I had rerere disabled at the time of commit. The new merge commit contains a few additional commits on the "ours" side of the merge (but they should not introduce new conflicts as they modified a different set of files).
For instance, take the following DAG:
m [master] Add new stuff
*
| o [old-master] Merge branch A (conflicts)
|/a [branch A]
n *
* *
*/
*
Now, what I want to do is to bring commits m and m^ into the branch old-master (and later make that the new master). I don't want to simply merge master into old-master, since it will create a new merge commit (albeit without conflicts). I want to recreate commit o with m and a as parents.
The new DAG should look like:
p [old-master] Merge branch A (same conflict resolution as old commit o)
/|
m | [master] Add new stuff
* |
| a [branch A]
n *
* *
*/
*
I don't mind using rerere, if I can tell it afterwards to record the resolution of the existing merge commit (o).
The simplest way to implement what you're asking for is probably to retroactively turn rerere on:
git config rerere.enabled true # with rerere turned on,
git checkout $o^1 # rerun the original merge
git merge $o^2
git read-tree --reset -u $o: # resolve conflicts exactly as before
git commit # throwaway commit to feed the results to rerere
and now that rerere has seen what you did with those conflicts,
git checkout -B old-master $o^1 # rewind `old-master` to before the merge
git merge master # rerun it with current ancestry