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
1189140909,I_kwDOAMm_X85G4Nmt,6434,concat along dim with mix of scalar coordinate and array coordinates is not right,2448579,closed,0,,,3,2022-04-01T02:29:16Z,2022-04-06T01:19:47Z,2022-04-06T01:19:47Z,MEMBER,,,,"### What happened?

Really hard to describe  in words =)

```
concat = xr.concat([da.isel(time=0), da.isel(time=[1])], dim=""time"")
xr.align(concat, da, dim=""time"")
```

fails when `concat` and `da` should be identical. This is causing failures in cf-xarray:https://github.com/xarray-contrib/cf-xarray/issues/319

cc @benbovy 


### What did you expect to happen?

_No response_

### Minimal Complete Verifiable Example

```Python
import numpy as np
import xarray as xr

time = xr.DataArray(
    np.array(
        [""2013-01-01T00:00:00.000000000"", ""2013-01-01T06:00:00.000000000""],
        dtype=""datetime64[ns]"",
    ),
    dims=""time"",
    name=""time"",
)

da = time
concat = xr.concat([da.isel(time=0), da.isel(time=[1])], dim=""time"")
xr.align(da, concat, join=""exact"")  #  works

da = xr.DataArray(np.ones(time.shape), dims=""time"", coords={""time"": time})
concat = xr.concat([da.isel(time=0), da.isel(time=[1])], dim=""time"")
xr.align(da, concat, join=""exact"")
```


### Relevant log output


```
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Input In [27], in <module>
     17 da = xr.DataArray(np.ones(time.shape), dims=""time"", coords={""time"": time})
     18 concat = xr.concat([da.isel(time=0), da.isel(time=[1])], dim=""time"")
---> 19 xr.align(da, concat, join=""exact"")

File ~/work/python/xarray/xarray/core/alignment.py:761, in align(join, copy, indexes, exclude, fill_value, *objects)
    566 """"""
    567 Given any number of Dataset and/or DataArray objects, returns new
    568 objects with aligned indexes and dimension sizes.
   (...)
    751 
    752 """"""
    753 aligner = Aligner(
    754     objects,
    755     join=join,
   (...)
    759     fill_value=fill_value,
    760 )
--> 761 aligner.align()
    762 return aligner.results

File ~/work/python/xarray/xarray/core/alignment.py:549, in Aligner.align(self)
    547 self.find_matching_unindexed_dims()
    548 self.assert_no_index_conflict()
--> 549 self.align_indexes()
    550 self.assert_unindexed_dim_sizes_equal()
    552 if self.join == ""override"":

File ~/work/python/xarray/xarray/core/alignment.py:395, in Aligner.align_indexes(self)
    393 if need_reindex:
    394     if self.join == ""exact"":
--> 395         raise ValueError(
    396             ""cannot align objects with join='exact' where ""
    397             ""index/labels/sizes are not equal along ""
    398             ""these coordinates (dimensions): ""
    399             + "", "".join(f""{name!r} {dims!r}"" for name, dims in key[0])
    400         )
    401     joiner = self._get_index_joiner(index_cls)
    402     joined_index = joiner(matching_indexes)

ValueError: cannot align objects with join='exact' where index/labels/sizes are not equal along these coordinates (dimensions): 'time' ('time',)
```

### Anything else we need to know?

_No response_

### Environment

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