improve readme, add gitignore

.gitignore

@@ -0,0 +1 @@
+__pycache__/

readme.md

@@ -7,7 +7,9 @@ Try to show updates for your used docker images.
 Requirements
 ------------
 
-TODO
+* Docker
+* docker-compose
+* Libraries: requirements.txt (`pip3 install -r requirements.txt` or docker ;))
 
 You need a directory containing your service directories. These services must have a docker-compose.yml to get checked.
 
@@ -25,11 +27,13 @@ Example:
 
 If there are files or directories without a docker-compse.yml, it will just notify you and ignore it. 
 
-
+If the compose file contains a build-section, the Dockerfile is inspected, too.
 
 Usage
 ----
 
+### Docker
+
 Modify mount of services directory. Mount your directory as `/services`.
 
 ```
@@ -38,21 +42,45 @@ docker-compose up
 
 Output file: `updates.json`
 
+### Command line
+
+```
+$ python3 show_updateable.py -h
+usage: show_updateable.py [-h] [--output OUTPUT]
+                          [--ignore IGNORE [IGNORE ...]] [--match-suffix]
+                          compose_files [compose_files ...]
+```
+
+* output: json file for results
+* ignore: ignore services (ignore is substring of service path)
+* match-suffix: use only same suffixes in image labels (e.g. only -alpine images)
+* compose files: service directories: see #example (multiple paths allowed)
 
 Advantages
 ----------
 
 * No access to Docker-Socket
+* No deamon
+* No state
+* Detect new major versions
+* Report only, no uncontrolled automated actions
 * tbc ...
 
 
 Alternatives
 ------------
 
-* https://github.com/v2tec/watchtower
+* https://github.com/v2tec/watchtower (seems quite dead, look for forks)
+* https://github.com/pyouroboros/ouroboros
 * https://engineering.salesforce.com/open-sourcing-dockerfile-image-update-6400121c1a
 * https://stackoverflow.com/questions/26423515/how-to-automatically-update-your-docker-containers-if-base-images-are-updated
 * tbc ...
 
 
+Known Issues
+------------
 
+* Still WiP/PoC
+* http/https sources are not implemented yet
+* some images have … weird tags
+* pull requests welcome