add hints about bug reporting and pull requests

CONTRIBUTING.md

@@ -1,14 +1,64 @@
 # Nominatim contribution guidelines
 
-## Workflow
+## Reporting Bugs
 
-We operate the "Fork & Pull" model explained at
+Bugs can be reported at https://github.com/openstreetmap/Nominatim/issues.
+Please always open a separate issue for each problem. In particular, do
+not add your bugs to closed issues. They may looks similar to you but
+often are completely different from the maintainer's point of view.
+
+### When Reporting Bad Search Results...
+
+Please make sure to add the following information:
+
+ * the URL of the query that produces the bad result
+ * the result you are getting
+ * the expected result, preferably a link to the OSM object you want to find,
+   otherwise an address that is as precise as possible
+ 
+ To get the link to the OSM object, you can try the following:
+ 
+ * go to https://openstreetmap.org
+ * zoom to the area of the map where you expect the result and
+   zoom in as much as possible
+ * click on the question mark on the right side of the map,
+   then with the queston cursor on the map where your object is located
+ * find the object of interest in the list that appears on the left side
+ * click on the object and report the URL back that the browser shows
+
+### When Reporting Problems with your Installation...
+
+Please add the following information to your issue:
+
+ * hardware configuration: RAM size, kind of disks
+ * Operating system (also mention if you are running on a cloud server)
+ * Postgres and Postgis version
+ * Nominatim version (commit id, if you run from the github repo)
+ * (if applicable) exact command line of the command that was causing the issues
+
+
+## Workflow for Pull Requests
+
+We love to get pull reuqests from you. We operate the "Fork & Pull" model
+explained at
 
 https://help.github.com/articles/using-pull-requests
 
 You should fork the project into your own repo, create a topic branch
 there and then make one or more pull requests back to the openstreetmap repository.
-Your pull requests will then be reviewed and discussed.
+Your pull requests will then be reviewed and discussed. Please be aware
+that you are responsible for your pull requests. You should be prepared
+to get change requests because as the maintainers we have to make sure
+that your contribution fits well with the rest of the code. Please make
+sure that you have time to react to these comments and amend the code or
+engage in a conversion. Do not expect that others will pick up your code,
+it will almost never happen.
+
+Please open a separate pull request for each issue you want to address.
+Don't mix multiple changes. In particular, don't mix style cleanups with
+feature pull requests. If you plan to make larger changes, please open
+an issue first or comment on the appropriate issue already existing so
+that duplicate work can be avoided.
 
 ## Coding style