initial draft for contributing.md

contributing.md

@@ -0,0 +1,101 @@
+# The git stuff
+
+[Guide by github, scroll down a bit](https://guides.github.com/activities/contributing-to-open-source/)
+
+# Deprecation
+
+Backward compatibility is important, so if you are renaming a proc or
+a type, you can use
+
+```nim
+{.deprecated [oldName: new_name].}
+```
+
+Or you can simply use
+
+```nim
+proc oldProc() {.deprecated.}
+```
+
+to mark a symbol as deprecated. Works for procs/types/vars/consts,
+etc.
+
+[Deprecated pragma in the manual.](http://nim-lang.org/docs/manual.html#pragmas-deprecated-pragma)
+
+# Writing tests
+
+Not all the tests follow this scheme, feel free to change the ones
+that don't. Always leave the code cleaner than you found it.
+
+## Stdlib
+
+If you change the stdlib (anything under `lib/`), put a test in the
+file you changed. Add the tests under an `when isMainModule:`
+condition so they only get executed when the tester is building the
+file. Each test should be in a separate `block:` statement, such that
+each has its own scope. Use boolean conditions and `assert` for the
+testing by itself, don't rely on echo statements or similar.
+
+Sample test:
+
+```nim
+when isMainModule:
+  block lenTest:
+    var values: HashSet[int]
+    assert(not values.isValid)
+    assert values.len == 0
+    assert values.card == 0
+  block setIterator:
+    type pair = tuple[a, b: int]
+    var a, b = initSet[pair]()
+    a.incl((2, 3))
+    a.incl((3, 2))
+    a.incl((2, 3))
+    for x, y in a.items:
+      b.incl((x - 2, y + 1))
+    assert a.len == b.card
+    assert a.len == 2
+```
+
+## Compiler
+
+The tests for the compiler work differently, they are all located in
+`tests/`. Each test has its own file, which is different from the
+stdlib tests. At the beginning of every test is the expected side of
+the test. Possible keys are:
+
+- output: The expected output, most likely via `echo`
+- exitcode: Exit code of the test (via `exit(number)`)
+- errormsg: The expected error message
+- file: The file the errormsg
+- line: The line the errormsg was produced at
+
+An example for a test:
+```nim
+discard """
+  errormsg: "type mismatch: got (PTest)"
+"""
+
+type
+  PTest = ref object
+
+proc test(x: PTest, y: int) = nil
+
+var buf: PTest
+buf.test()
+```
+
+# Running tests
+
+You can run the tests with
+
+    ./koch tests
+
+which will run a good subset of tests. Some tests may fail.
+
+# Comparing tests
+
+Because some tests fail in the current `devel` branch, not every fail
+after your change is necessarily caused by your changes.
+
+TODO