prompt bug fix

doc/CHANGELOG.md

@@ -119,6 +119,20 @@ Versions follow `MAJOR.MINOR.PATCH-REVISION_STAGE_N` (e.g. `3.99.1-4_rc_1`).
   child, validates the PID and refuses the current shell; `ppn` matched PIDs
   and names such as `kde-bash` (now exact); `ppg`/`gpid` fallbacks no longer
   match their own `awk`; `PPU_DEFAULT_FORMAT` documented with its real value.
+- `prompt.sh` (security): a git branch, conda environment or virtualenv named
+  like `x$(command)` was **executed** each time the prompt was drawn, because the
+  names were copied into `PS1`; the context segment is now referenced as a
+  variable and never re-expanded.
+- `prompt.sh`: the exit status shown in the prompt was always `0` (the nested
+  function definitions at the top of `set_prompt` reset `$?`; they are now
+  defined once at load time); `PROMPT_COLOR_*` overrides of the `[prompt]`
+  section never beat the theme and `$ColorName` values were emptied by
+  `parse_conf` in a fresh login shell (now resolved, validated, and re-applied
+  after `set_theme`); `set_theme --preview` left the previewed colours behind
+  when none were set before, and a switch to a partial theme kept the previous
+  theme's colours; the prompt no longer forks `date` twice per command
+  (`$EPOCHREALTIME`) and runs one `git status` instead of three git commands,
+  without taking the index lock.
 - `compress.sh`: option flags and loop variables no longer leak into the
   interactive shell.