demos: fix terminal width for screenshots

demos/helpers.sh

@@ -11,7 +11,9 @@ new_tmp_dir() {
 
 run_command() {
   echo "\$ $@"
-  eval "$@"
+  # `bash` often resets $COLUMNS, so we also
+  # allow $RUN_COMMAND_COLUMNS
+  COLUMNS=${RUN_COMMAND_COLUMNS-${COLUMNS-80}} eval "$@"
 }
 
 run_command_allow_broken_pipe() {

demos/run_script.sh

@@ -16,6 +16,16 @@ GIT_CONFIG_GLOBAL=$(mktemp --tmpdir gitconfig-XXXX)
 export GIT_CONFIG_GLOBAL
 git_config "$GIT_CONFIG_GLOBAL"
 
+# Make `jj` wrap text as opposed to `term-transcript`
+# Currently, 80 is the only value the tool supports when
+# used as a CLI.
+# https://github.com/slowli/term-transcript/issues/59
+#
+# Note that `bash` likes to reset the value of $COLUMNS,
+# so we need to use a different variable here.
+RUN_COMMAND_COLUMNS=80
+export RUN_COMMAND_COLUMNS
+
 for script in "$@"; do
   script_base="${script%.sh}"
   script_base="${script_base#demo_}"