Checks that squash and merge do the same thing, with nontrivial history that
includes a merge conflict.

```unison
x.a.a = "af"
```

```ucm

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:
  
    ⍟ These new definitions are ok to `add`:
    
      x.a.a : Text

```
```ucm
.> add

  ⍟ I've added these definitions:
  
    x.a.a : Text

.> fork x y

  Done.

.> fork x s

  Done.

.> fork x m

  Done.

.> delete y.a.a

  Name changes:
  
    Original    Changes
    1. m.a.a ┐  2. y.a.a (removed)
    3. s.a.a │  
    4. x.a.a │  
    5. y.a.a ┘  
  
  Tip: You can use `undo` or `reflog` to undo this change.

```
```unison
y.a.a = "fij"
```

```ucm

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:
  
    ⍟ These new definitions are ok to `add`:
    
      y.a.a : Text

```
```ucm
.> add

  ⍟ I've added these definitions:
  
    y.a.a : Text

```
```unison
y.b.a = "wie"
```

```ucm

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:
  
    ⍟ These new definitions are ok to `add`:
    
      y.b.a : Text

```
```ucm
.> add

  ⍟ I've added these definitions:
  
    y.b.a : Text

.> merge y.b y.a

  Here's what's changed in y.a after the merge:
  
  New name conflicts:
  
    1. a#a3ef1630bu : Text
       ↓
    2. ┌ a#a3ef1630bu : Text
    3. └ a#fjqpdmdeqi : Text
  
  Tip: You can use `todo` to see if this generated any work to
       do in this namespace and `test` to run the tests. Or you
       can use `undo` or `reflog` to undo the results of this
       merge.

.> delete.term 1

  Resolved name conflicts:
  
    1. ┌ y.a.a#a3ef1630bu : Text
    2. └ y.a.a#fjqpdmdeqi : Text
       ↓
    3. y.a.a#fjqpdmdeqi : Text
  
  Tip: You can use `undo` or `reflog` to undo this change.

.> merge y m

  Here's what's changed in m after the merge:
  
  Updates:
  
    1. a.a : Text
       ↓
    2. a.a : Text
  
  Added definitions:
  
    3. ┌ a.a : Text
    4. └ b.a : Text
  
  Tip: You can use `todo` to see if this generated any work to
       do in this namespace and `test` to run the tests. Or you
       can use `undo` or `reflog` to undo the results of this
       merge.

.> squash y s

  Here's what's changed in s after the merge:
  
  New name conflicts:
  
    1. a.a#0gr1q8f2jk : Text
       ↓
    2. ┌ a.a#0gr1q8f2jk : Text
    3. └ a.a#fjqpdmdeqi : Text
  
  Added definitions:
  
    4. ┌ a.a#fjqpdmdeqi : Text
    5. └ b.a            : Text
  
  Tip: You can use `todo` to see if this generated any work to
       do in this namespace and `test` to run the tests. Or you
       can use `undo` or `reflog` to undo the results of this
       merge.

.s> todo

  ❓
  
  These terms have conflicting definitions: a.a
  
  Tip: This occurs when merging branches that both independently
       introduce the same name. Use `view a.a` to see the
       conflicting defintions, then use `move.term` to resolve
       the conflicts.

```