unison/unison-src/transcripts/diff.md

```ucm:hide
.> builtins.mergeio
```

```unison:hide
x = 23
```

```ucm
.b1> add
.b1> alias.term x fslkdjflskdjflksjdf
.> fork b1 b2
.b2> alias.term x abc
```
```unison:hide
fslkdjflskdjflksjdf = 663
```
```ucm
.b0> add
.> merge b0 b1
.> diff.namespace b1 b2
```
Things we want to test:

* Diffing identical namespaces
* Adds, removes, updates (with and without metadata updates)
  * Adds with multiple names
  * Adds with multiple names and different metadata on each
* Moved and copied definitions
  * Moves that have more that 1 initial or final name
* ... terms and types
* New patches, modified patches, deleted patches, moved patches
* With and without propagated updates

```unison:hide
fromJust = 1
b = 2
bdependent = b
c = 3
helloWorld = "Hello, world!"

type A a = A Nat
ability X a1 a2 where x : Nat
```

```ucm
.ns1> add
.ns1> alias.term fromJust fromJust'
.ns1> alias.term helloWorld helloWorld2
.ns1> link b fromJust
.ns1> fork .ns1 .ns2
.ns1> cd .
```
Here's what we've done so far:
```ucm
.> diff.namespace nothing ns1
.> diff.namespace ns1 ns2
```

```unison:hide
fromJust = "asldkfjasldkfj"
```

```ucm
.ns1b> add
.> merge ns1b ns1
```

```unison:hide
fromJust = 99
b = "oog"
d = 4
e = 5
f = 6
unique type Y a b = Y a b
```

```ucm
.ns2> update
.ns2> links fromJust
.> diff.namespace ns1 ns2
.> alias.term ns2.d ns2.d'
.> alias.type ns2.A ns2.A'
.> alias.type ns2.X ns2.X'
.> diff.namespace ns1 ns2
.> link ns1.c ns2.f
.> link ns2.c ns2.c
.> diff.namespace ns1 ns2
.> unlink ns2.b ns2.fromJust
.> diff.namespace ns1 ns2
.> alias.type ns1.X ns1.X2
.> alias.type ns2.A' ns2.A''
.> view.patch ns2.patch
.> fork ns2 ns3
.> alias.term ns2.fromJust' ns2.yoohoo
.> delete.term ns2.fromJust'
.> diff.namespace ns3 ns2
```
```unison:hide
bdependent = "banana"
```
```ucm
.ns3> update
.> diff.namespace ns2 ns3
```


## Two different auto-propagated changes creating a name conflict
Currently, the auto-propagated name-conflicted definitions are not explicitly
shown, only their also-conflicted dependency is shown.
```unison:hide
a = 333
b = a + 1
```
```ucm
.nsx> add
.> fork nsx nsy
.> fork nsx nsz
```
```unison:hide
a = 444
```
```ucm
.nsy> update
```
```unison:hide
a = 555
```
```ucm
.nsz> update
.> merge nsy nsw
```
```ucm:error
.> merge nsz nsw
```
```ucm
.> diff.namespace nsx nsw
.nsw> view a b
```
```unison
a = 777
```

```ucm:error
.nsw> update
.nsw> view a b
```

##

Updates:  -- 1 to 1

New name conflicts: -- updates where RHS has multiple hashes (excluding when RHS=LHS)

  1. foo#jk19sm5bf8 : Nat - do we want to force a hashqualified? Arya thinks so
     ↓
  2. ┌ foo#0ja1qfpej6 : Nat
  3. └ foo#jk19sm5bf8 : Nat

Resolved name conflicts: -- updates where LHS had multiple hashes and RHS has one

  4. ┌ bar#0ja1qfpej6 : Nat
  5. └ bar#jk19sm5bf8 : Nat
     ↓
  6. bar#jk19sm5bf8 : Nat

## Display issues to fixup

- [d] Do we want to surface new edit conflicts in patches?
- [t] two different auto-propagated changes creating a name conflict should show
      up somewhere besides the auto-propagate count
- [t] Things look screwy when the type signature doesn't fit and has to get broken
      up into multiple lines. Maybe just disallow that?
- [d] Delete blank line in between copies / renames entries if all entries are 1 to 1
      see todo in the code
- [x] incorrectly calculated bracket alignment on hashqualified "Name changes"  (delete.output.md)
- [x] just handle deletion of isPropagated in propagate function, leave HandleInput alone (assuming this does the trick)
- [x] might want unqualified names to be qualified sometimes:
- [x] if a name is updated to a not-yet-named reference, it's shown as both an update and an add
- [x] similarly, if a conflicted name is resolved by deleting the last name to
      a reference, I (arya) suspect it will show up as a Remove
- [d] Maybe group and/or add headings to the types, constructors, terms
- [x] check whether creating a name conflict + adding metadata puts the update
      in both categories; if it does, then filter out metadataUpdates from the
      other categories
- [x] add tagging of propagated updates to test propagated updates output
- [x] missing old names in deletion ppe (delete.output.md)  (superseded by \#1143)
- [x] delete.term has some bonkers output
- [x] Make a decision about how we want to show constructors in the diff
- [x] When you delete a name with metadata, it also shows up in updates section
      with the deleted metadata.
- [x] An add with new metadata is getting characterized as an update
- [x] can there be a metadata-only update where it's not a singleton old and new reference
- [x] 12.patch patch needs a space
- [x] This looks like garbage
- [x] Extra 2 blank lines at the end of the add section
- [x] Fix alignment issues with buildTable, convert to column3M (to be written)
- [x] adding an alias is showing up as an Add and a Copy; should just show as Copy
- [x] removing one of multiple aliases appears in removes + moves + copies section
- [x] some overlapping cases between Moves and Copies^
- [x] Maybe don't list the type signature twice for aliases?