Breeze should load local tmux configuration in 'breeze start-airflow' (…

…apache#15454)

(cherry picked from commit 508cd39)

BREEZE.rst

@@ -258,11 +258,26 @@ You should set up the autocomplete option automatically by running:
 
 You get the auto-completion working when you re-enter the shell.
 
+Customize your environment
+--------------------------
 When you enter the Breeze environment, automatically an environment file is sourced from
 ``files/airflow-breeze-config/variables.env``. The ``files`` folder from your local sources is
 automatically mounted to the container under ``/files`` path and you can put there any files you want
 to make available for the Breeze container.
 
+You can also add your local tmux configuration in ``files/airflow-breeze-config/.tmux.conf`` and
+these configurations will be available for your tmux environment.
+
+there is a symlink between ``files/airflow-breeze-config/.tmux.conf`` and ``~/.tmux.conf`` in the container,
+so you can change it at any place, and run
+
+.. code-block:: bash
+
+  tmux source ~/.tmux.conf
+
+inside container, to enable modified tmux configurations.
+
+
 .. raw:: html
 
     <div align="center">

scripts/in_container/configure_environment.sh

@@ -19,6 +19,7 @@
 export FILES_DIR="/files"
 export AIRFLOW_BREEZE_CONFIG_DIR="${FILES_DIR}/airflow-breeze-config"
 VARIABLES_ENV_FILE="variables.env"
+TMUX_CONF_FILE=".tmux.conf"
 
 if [[ -d "${FILES_DIR}" ]]; then
     export AIRFLOW__CORE__DAGS_FOLDER="/files/dags"
@@ -48,3 +49,20 @@ else
     echo "In it to make breeze source the variables automatically for you"
     echo
 fi
+
+
+if [[ -d "${AIRFLOW_BREEZE_CONFIG_DIR}" && \
+    -f "${AIRFLOW_BREEZE_CONFIG_DIR}/${TMUX_CONF_FILE}" ]]; then
+    pushd "${AIRFLOW_BREEZE_CONFIG_DIR}" >/dev/null 2>&1 || exit 1
+    echo
+    echo "Using ${TMUX_CONF_FILE} from ${AIRFLOW_BREEZE_CONFIG_DIR}"
+    echo
+     # shellcheck disable=1090
+    ln -sf "${AIRFLOW_BREEZE_CONFIG_DIR}/${TMUX_CONF_FILE}" ~
+    popd >/dev/null 2>&1 || exit 1
+else
+    echo
+    echo "You can add ${AIRFLOW_BREEZE_CONFIG_DIR} directory and place ${TMUX_CONF_FILE}"
+    echo "in it to make breeze use your local ${TMUX_CONF_FILE} for tmux"
+    echo
+fi