Add option to exit immediately (#13)

* Add zero interval escape to entry point

* Update README.md

* Update README.md and entrypoint.sh to clarify RENEWAL_INTERVAL behavior

- Revised the description of the `RENEWAL_INTERVAL` environment variable in README.md to specify that setting it to `0` disables renewals and runs the process only once.
- Enhanced entrypoint.sh with a message indicating that Let's Encrypt renewals are disabled when `RENEWAL_INTERVAL` is set to `0`, improving user awareness of the configuration's impact.

---------

Co-authored-by: Jay Rogers <[email protected]>

Author: mmeyer2k

README.md

@@ -44,7 +44,7 @@ The following environment variables can be used to customize the Certbot contain
 | `DEBUG`                | Enable debug mode (prints more information to the console)            | `false`                    |
 | `PUID`                 | The user ID to run certbot as                                       | `0`                    |
 | `PGID`                 | The group ID to run certbot as                                        | `0`                    |
-| `RENEWAL_INTERVAL`     | Interval between certificate renewal checks                         | 43200 seconds (12 hours) |
+| `RENEWAL_INTERVAL`     | Interval between certificate renewal checks. Set to `0` to disable renewals and only run once.                         | 43200 seconds (12 hours) |
 | `REPLACE_SYMLINKS`     | Replaces symlinks with direct copies of the files they reference (required for Windows) | `false`                    |
 
 ## Usage
@@ -155,4 +155,4 @@ If you appreciate this project, be sure to check out our other projects.
 ### 🌍 Open Source
 - **[AmplitudeJS](https://521dimensions.com/open-source/amplitudejs)**: Open-source HTML5 & JavaScript Web Audio Library.
 - **[Spin](https://serversideup.net/open-source/spin/)**: Laravel Sail alternative for running Docker from development → production.
-- **[Financial Freedom](https://github.com/serversideup/financial-freedom)**: Open source alternative to Mint, YNAB, & Monarch Money.
+- **[Financial Freedom](https://github.com/serversideup/financial-freedom)**: Open source alternative to Mint, YNAB, & Monarch Money.

src/entrypoint.sh

@@ -193,6 +193,12 @@ else
     # Run certbot initially to get the certificates
     run_certbot
 
+    # If RENEWAL_INTERVAL is set to 0, do not attempt to renew certificates and exit immediately
+    if [ "$RENEWAL_INTERVAL" = "0" ]; then
+        echo "Let's Encrypt Renewals are disabled because RENEWAL_INTERVAL=0. Running once and exiting..."
+        cleanup
+    fi
+
     # Infinite loop to keep the container running and periodically check for renewals
     while true; do
         # POSIX-compliant way to show next run time