id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
627356505,MDU6SXNzdWU2MjczNTY1MDU=,4110,Feature request: merge compat overlap,34353851,open,0,,,1,2020-05-29T15:36:29Z,2021-04-19T14:46:46Z,,NONE,,,,"`xarray.merge` should have an option compat overlap.
is that option is combine_first, but it has more sense inside of merge.
```python
import xarray as xr
x1=xr.DataArray([1,2,3,4,11],dims=['time'],coords=[[4,5,6,7,3]]).to_dataset(name='fusionfria')
x2=xr.DataArray([5,6,7,8],dims=['time'],coords=[[0,1,2,3]]).to_dataset(name='fusionfria')
x1.combine_first(x2)
```

It could be useful to avoid the error in xarray.open_mfdataset, if the time index is overlapped between netcdf files.

ValueError: Resulting object does not have monotonic global indexes along dimension time","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4110/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue