starship: put chezmoi diff status in the prompt

home/dot_config/starship.toml

@@ -1,6 +1,6 @@
 "$schema" = 'https://starship.rs/config-schema.json'
 
-format = '$time$line_break$all$line_break$character'
+format = '$time$custom$line_break$all$line_break$character'
 
 [cmd_duration]
 show_milliseconds = true
@@ -60,6 +60,13 @@ style = 'yellow'
 threshold = 66
 style = 'dimmed green'
 
+[custom.chezmoi_diff]
+description = 'Size of the current "chezmoi diff" output'
+command = 'cat ~/.cache/chezmoi-diff-count'
+when = 'test -s ~/.cache/chezmoi-diff-count'
+symbol = '  '
+disabled = false
+
 # The symbols below were produced by `starship preset nerd-font-symbols`, then moved to sections above, as needed.
 [aws]
 symbol = "  "

home/dot_config/systemd/user/chezmoi-diff.service

@@ -0,0 +1,6 @@
+[Unit]
+Description=Record size of 'chezmoi diff' output
+
+[Service]
+Type=oneshot
+ExecStart=/bin/sh -c 'chezmoi diff | wc -l > ~/.cache/chezmoi-diff-count'

home/dot_config/systemd/user/chezmoi-diff.timer

@@ -0,0 +1,9 @@
+[Unit]
+Description=Periodically count chezmoi differences
+
+[Timer]
+OnBootSec=5m
+OnUnitInactiveSec=5m
+
+[Install]
+WantedBy=timers.target

home/dot_config/systemd/user/timers.target.wants/symlink_chezmoi-diff.timer

@@ -0,0 +1 @@
+../chezmoi-diff.timer