demos: make jj perform the line wrapping instead of term-transcript

Previously, `jj` couldn't determine the terminal widths inside demos.

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_scripts.sh

@@ -25,6 +25,15 @@ which convert > /dev/null \
 echo "jj --version: (set PATH to change)"
 jj --version
 
+# Make `jj` wrap text as opposed to `term-transcript`. `term-transcript` wraps
+# at 80 columns. Also, 80 seems to be the maximum number of columns that's
+# somewhat readable on mobile devices.
+#
+# Note that `bash` likes to reset the value of $COLUMNS, so we use a different
+# variable here that is interpreted by `run_command()` in `helpers.sh`.
+RUN_COMMAND_COLUMNS=80
+export RUN_COMMAND_COLUMNS
+
 run_script_through_term_transcript_and_pipe_result_to_stderr() {
   script="$1"
   script_base="${script%.sh}"

demos/setup_standard_config.sh

@@ -17,6 +17,7 @@ username = "jjfan"
 [ui]
 color="always"
 paginate="never"
+log-word-wrap=true  # Need to set COLUMNS for this to work
 EOF
 
 GIT_CONFIG_GLOBAL=$(mktemp --tmpdir gitconfig-XXXX)