demos: update demos as little as possible to regenerate them

This updates demos to the point where they can run without
warnings. Some of them become less clear, this is addressed
(where I noticed it) in follow-up commits.

Fixes jj-vcs#3209

demos/demo_juggle_conflicts.sh

@@ -14,7 +14,7 @@ new_tmp_dir
     echo "third" > file
     jj branch create third
     jj commit -m 'third'
-) >/dev/null
+) >/dev/null 2>&1
 
 comment "We are in a repo with three commits, all
 editing the same line:"
@@ -33,13 +33,13 @@ interesting is that the top commit has no conflict! That's because it
 has the changes from all three commits applied to it.
 
 Let's verify that by looking at its contents:"
-run_command "jj co second"
+run_command "jj new second"
 run_command "cat file"
 
 comment "Let's now instead make \"second\" and \"third\"
 sibling and merge them:"
 run_command "jj rebase -s second -d first"
-run_command "jj merge second third -m merged"
+run_command "jj new second third -m merged"
 run_command "jj log"
 comment "Again, because the merge commit has the
 changes from all three commits, it has no

demos/demo_operation_log.sh

@@ -6,9 +6,10 @@ new_tmp_dir
 {
     jj git clone https://github.com/octocat/Hello-World
     cd Hello-World
-    jj abandon octocat-patch-1
+    jj abandon --ignore-immutable octocat-patch-1@origin
     jj branch forget octocat-patch-1
-} > /dev/null
+    jj branch track test@origin
+} > /dev/null 2>&1
 
 comment "We are in the octocat/Hello-World repo.
 The \"operation log\" shows the operations
@@ -24,7 +25,7 @@ run_command "jj rebase -d test"
 
 comment "We are now going to make another change off of
 master:"
-run_command "jj co master"
+run_command "jj new master"
 run_command "jj describe -m \"other stuff\""
 
 comment "The repo now looks like this:"

demos/demo_resolve_conflicts.sh

@@ -6,9 +6,9 @@ new_tmp_dir
 {
     jj git clone https://github.com/octocat/Hello-World 
     cd Hello-World
-    jj abandon test
+    jj abandon --ignore-immutable test@origin
     jj branch forget test
-} > /dev/null
+} > /dev/null 2>&1
 
 comment "We are on the master branch of the
 octocat/Hello-World repo:"

demos/demo_working_copy.sh

@@ -6,11 +6,11 @@ new_tmp_dir
 {
     jj git clone https://github.com/octocat/Hello-World
     cd Hello-World
-    jj abandon test
+    jj abandon --ignore-immutable test@origin
     jj branch forget test
-    jj abandon octocat-patch-1
+    jj abandon --ignore-immutable octocat-patch-1@origin
     jj branch forget octocat-patch-1
-}> /dev/null
+}> /dev/null 2>&1
 
 comment "We are in the octocat/Hello-World repo.
 We have an empty working copy on top of master:"
@@ -31,7 +31,7 @@ run_command "jj branch create goodbye"
 run_command "jj log"
 
 comment "Start working on a new change off of master:"
-run_command "jj co master"
+run_command "jj new master"
 comment "Note that we were told the working copy is now empty (AKA clean). The
 \"goodbye\" change stayed in its own commit:"