Add undo.md transcript

unison-src/transcripts/undo.md

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+# Undo
+
+Undo should pop a node off of the history of the current branch.
+
+```unison:hide
+x = 1
+```
+
+```ucm
+scratch/main> builtins.merge lib.builtins
+scratch/main> add
+scratch/main> ls
+scratch/main> alias.term x y
+scratch/main> ls
+scratch/main> history
+scratch/main> undo
+scratch/main> ls
+scratch/main> history
+```
+
+---
+
+It should not be affected by changes on other branches.
+
+```unison:hide
+x = 1
+```
+
+```ucm
+scratch/branch1> builtins.merge lib.builtins
+scratch/branch1> add
+scratch/branch1> ls
+scratch/branch1> alias.term x y
+scratch/branch1> ls
+scratch/branch1> history
+-- Make some changes on an unrelated branch
+scratch/branch2> builtins.merge lib.builtins
+scratch/branch2> delete.namespace lib
+scratch/branch1> undo
+scratch/branch1> ls
+scratch/branch1> history
+```
+
+---
+
+Undo should be a no-op on a newly created branch
+
+```ucm:error
+scratch/main> branch.create-empty new
+scratch/new> undo
+```

unison-src/transcripts/undo.output.md

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+# Undo
+
+Undo should pop a node off of the history of the current branch.
+
+```unison
+x = 1
+```
+
+```ucm
+scratch/main> builtins.merge lib.builtins
+
+  Done.
+
+scratch/main> add
+
+  ⍟ I've added these definitions:
+  
+    x : Nat
+
+scratch/main> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+
+scratch/main> alias.term x y
+
+  Done.
+
+scratch/main> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+  3. y    (Nat)
+
+scratch/main> history
+
+  Note: The most recent namespace hash is immediately below this
+        message.
+  
+  ⊙ 1. #nmem6r6no1
+  
+    + Adds / updates:
+    
+      y
+    
+    = Copies:
+    
+      Original name New name(s)
+      x             y
+  
+  ⊙ 2. #3rqf1hbev7
+  
+    + Adds / updates:
+    
+      x
+  
+  □ 3. #ms9lggs2rg (start of history)
+
+scratch/main> undo
+
+  Here are the changes I undid
+  
+  Name changes:
+  
+    Original  Changes
+    1. x      2. y (added)
+
+scratch/main> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+
+scratch/main> history
+
+  Note: The most recent namespace hash is immediately below this
+        message.
+  
+  ⊙ 1. #3rqf1hbev7
+  
+    + Adds / updates:
+    
+      x
+  
+  □ 2. #ms9lggs2rg (start of history)
+
+```
+---
+
+It should not be affected by changes on other branches.
+
+```unison
+x = 1
+```
+
+```ucm
+scratch/branch1> builtins.merge lib.builtins
+
+  Done.
+
+scratch/branch1> add
+
+  ⍟ I've added these definitions:
+  
+    x : Nat
+
+scratch/branch1> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+
+scratch/branch1> alias.term x y
+
+  Done.
+
+scratch/branch1> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+  3. y    (Nat)
+
+scratch/branch1> history
+
+  Note: The most recent namespace hash is immediately below this
+        message.
+  
+  ⊙ 1. #nmem6r6no1
+  
+    + Adds / updates:
+    
+      y
+    
+    = Copies:
+    
+      Original name New name(s)
+      x             y
+  
+  ⊙ 2. #3rqf1hbev7
+  
+    + Adds / updates:
+    
+      x
+  
+  □ 3. #ms9lggs2rg (start of history)
+
+-- Make some changes on an unrelated branch
+scratch/branch2> builtins.merge lib.builtins
+
+  Done.
+
+scratch/branch2> delete.namespace lib
+
+  Done.
+
+scratch/branch1> undo
+
+  Here are the changes I undid
+  
+  Name changes:
+  
+    Original  Changes
+    1. x      2. y (added)
+
+scratch/branch1> ls
+
+  1. lib/ (469 terms, 74 types)
+  2. x    (Nat)
+
+scratch/branch1> history
+
+  Note: The most recent namespace hash is immediately below this
+        message.
+  
+  ⊙ 1. #3rqf1hbev7
+  
+    + Adds / updates:
+    
+      x
+  
+  □ 2. #ms9lggs2rg (start of history)
+
+```
+---
+
+Undo should be a no-op on a newly created branch
+
+```ucm
+scratch/main> branch.create-empty new
+
+  Done. I've created an empty branch scratch/new.
+  
+  Tip: Use `merge /somebranch` to initialize this branch.
+
+scratch/new> undo
+
+  ⚠️
+  
+  Nothing more to undo.
+
+```