Project setup

.github/copilot-instructions.md

@@ -1,3 +1,33 @@
 # C2
 C2 is a compiler for a new language.
 See the README.md for information about this project.
+
+## Code Changes
+After every code change, ensure the binary builds correctly,
+and run the unit tests (`make test`).
+
+Ensure that every new function and code path has useful unit tests.
+
+### Creating Source Files
+Whenever a new source file is created, it must be added to the `include.mk` file.
+A test file should also be created.
+
+Test source files do not have to be added to the include.mk file.
+These are added to the `test.c` file by means of directly `#include`ing the C file.
+
+### Testing
+Any test source code must be prefixed with test_xyz, where xyz matches
+the source file it is trying to test.
+For instance, a test for `buffer.c` must be called `test_buffer.c`.
+
+There will be no `test_buffer.h`. Instead, `test.c` will directly
+`#include` the C–source-file directly.
+
+## Language Syntax
+Since this is a compiler for a new language, do not assume anything
+of its syntax.
+Always check the `specs` directory.
+
+If there is anything unclear, ask the user for clarification.
+It is certainly possible that there are contradictions in the
+spec that have to be solved first.