add timeout to git operations

README.md

@@ -356,6 +356,7 @@ The twelve available `PROMPT_COLOR_*` keys are:
 [prompt]
 PROMPT_SHOW_GIT   = 1
 PROMPT_SHOW_GIT_STATUS = 1
+PROMPT_GIT_TIMEOUT = 2
 PROMPT_SHOW_CONDA = 1
 PROMPT_SHOW_VENV  = 1
 PROMPT_SHOW_SESSION = 1
@@ -366,10 +367,11 @@ When enabled, the top prompt bar appends:
 - `git:<branch>` when inside a Git repository
 - `git:<branch>*` when local changes are present
 - `git:<branch> +N/-M` when ahead/behind upstream
+- `git:<branch>?` when `git diff` or `git rev-list` exceeded `PROMPT_GIT_TIMEOUT`
 - `conda:<env>` when a Conda environment is active
 - `venv:<name>` when a Python virtualenv is active (and Conda is not)
 - `ssh`, `tmux`, `screen` markers when the session runs in those contexts
-- both, separated by `|`, when both are available
+- all, separated by `|`, when several are available
 
 **Writing a custom theme file:**